Isabel sat down in front of one of the consoles. Marisa occupied the one that was free. The rest of us stood behind. From her seat, Isabel observed the changing images of the laborious search for the rupture point that the computers were trying to locate by historical comparison. The system is relatively simple; one just needs to begin searching back starting from 7 August 2012. At first, events differ quite a bit from history as we know it, but little by little the changes start merging toward zero and history more closely resembles the real one. Besides, in this case, we also had the advantage of knowing, through some preliminary automatic analyses, that the change had happened at the Transition. Each console is connected simultaneously to our own databases, to history as it happened, and to the external database, which allows us to compare the records.

The entire TIC General Headquarters, which in turn depends on the Spanish Intelligence Group, is enclosed in an ecstasis field. This means that we notice the changes in history only by comparing our records to those on the outside; for those of us who are inside the chamber, the change that had altered life in the outside world had not taken place and we remembered history just as it had happened. The existence of the ecstasis field means that we are virtually trapped in the building. We can leave, yes, but we cannot lead an independent life. If we were to live outside without protection, history's tidal wave would end up engulfing us. We would end up living a particular version of the universe and we would lose our effectiveness as agents. No, we may spy on the world, on outside reality, but we can't really enjoy it.

The theory that allows for time travel is probably the strangest of the whole history of physics; it's difficult to understand and it's based on an incredible number of equations. It is the basis for a great unification theory that some day will explain everything but that, for now, allows us to travel through time using reasonable quantities of energy. It is simply called Temporal Theory, or TT. Unfortunately, some of the effects caused by the theory are almost metaphysical. When it was formulated, when that young physicist finally comprehended it and conceived it pure and whole for the first time, the theory changed the nature of the universe and of reality itself. Before 7 August 2012 only one temporal line existed. There was only one history, shared by all. That August afternoon, exactly at the moment the theory was definitively formulated, time became multiple; temporal lines started to diverge as quanta phenomenawere happening in the universe. There are now infinite histories, most of them almost identical, globally indistinguishable with only trivial details to differentiate them; yet others are very different. Exact copies of each human being on Earth live in many-in billions of them.

Philosophers and physicists have spent years trying to explain this, and they haven't gotten very far. It is clear, though, that the first quantum physicists were right: the observer has an effect on the observed, and the existence of intelligent beings in the cosmos alters the workings of the universe. How else to explain this situation? Five minutes before one August day there was only one history, and five minutes afterward there were millions. Furthermore, those temporal lines are real and may be visited easily. The same technology that allows time travel allows taking a trip among alternative temporal lines.

In 1955, Hugh Everett formulated what was called the "many worlds interpretation" of quantum mechanics. According to him, each time a phenomenon of quantum scale occurred, the universe divided itself into as many versions as were necessary to account for all possible results. In the simplest case, there were two possibilities: on one branch the process had happened, and on the other it hadn't. But now one could say that Everett was both right and wrong at the same time. Before the summer of 2012, the universe, in the simplest, two-option case, accepted one of those phenomena and discarded the other one. But after that summer, the universe executes all the possibilities and Everett is proven correct. Since 7 August 2012, the universe divides itself into as many universes as are necessary to cover all possibilities.

The ecstasis field surrounding the Temporal Intervention Center, which is based on a weird property of what physicists call imaginary time, allows those of us inside to experience only one past. If someone changes history, we continue to remember history just as it was, which lets us perceive when it has been manipulated. Unfortunately, the ecstasis field was a late byproduct of the theory, and by the time it was developed it was already too late-although I'm not sure what could have been done differently: surround the entire universe with an ecstasis field?

One thing we can be certain about is that this theory proves we are alone in the universe. At least that there is no extraterrestrial civilization at our stage of development. If there were a more advanced civilization, their physicists would have discovered Temporal Theory before and we would now see that the temporal divergences in the universe began at an earlier date than our own discovery of the theory.

Since that isn't the case, the conclusion is that we are alone, or at least, that we are the most advanced in the entire universe. It's not as surprising as it seems: someone had to be the first.

"I've got it," Jose Luis said out loud to get our attention.

We all crowded around his console. The computers had located the change point. On his screen was the 28 February 1977 front page of El Pais. In the version we had on our database-the version of history as it had really happened-the headlines were the usual ones for the time period. The version we had from the outside had only one headline that covered the whole first page: Carrillo Murdered. The newspaper from the day before was identical to our version, but the one for the following day had that ominous news eclipsing all the rest.

"This is new, isn't it?" said Rudy.

Nobody acknowledged him; he really wasn't looking for an answer.

"Poor man, that was all he needed. They've done just about everything else to him." Rudy continued.

During our training they teach us many of the tricks used to change the past. Almost all of them follow the same plan, killing some well-known person. Almost invariably they're the same people: Hitler, Stalin, Kennedy. But Rudy was right: they hadn't tried to kill Carrillo during that interview, which was odd, considering the many times the Communist leader was manipulated in one sense or another.

"We'd better look some more. Return to your consoles and continue searching. This is too obvious,"

I said.

Each one of us tried to find data that would link Carrillo with that date. With the information from the newspaper article, and from later ones that dealt with the news, we soon had a more or less clear idea of what had transpired. But we did not find any other point of change that wasn't caused by the assassination of the Spanish Communist Party's leader. I started to compare data. President Suarez had arranged a secret interview with Carrillo for 27 February. At that time, the Communist Party hadn't been legalized yet-that was still a couple of months away-and, for the Spain of the times, to have an interview with the CP's secretary-general was to have a date with the devil himself. It seems incredible now, but back then the Communist Party had great moral weight in Spanish society, and counting on the Communists was essential for the consolidation of democracy, but acting with too much haste could bring about serious consequences. Suarez understood this, but he also knew that if he could legalize the Communist Party and celebrate free elections with the whole political spectrum, he would gain strength and prestige. For that reason he arranged that ultra-secret interview; only the king and a couple of government members were in the know. The meeting itself wasn't very important, but if it had been discovered, the still-strong Francoist structures would have forced the fall of Suarez and delayed or stopped the advent of democracy.

"That's odd...It's been more than three years since Carrillo wasn't murdered," said Isabel in her characteristically soft voice.

At five in the afternoon they picked Carrillo up from his apartment in the Puente de Vallecas. He was driven down a hidden road. A person-a woman-took him to the Santa Ana cottage in the outskirts of Madrid, a quiet place. In real history, Suarez arrived a few minutes later and they both talked for hours about Politics with a capital "P." What the terrorists had done was very elementary. They had simply blown up Carrillo's car just before it got to the house. They were thus assured of two things: that the Bunker would know of this interview and that the Communist Party would be enraged about their leader's death. Weren't government members the only ones that knew of this supersecret interview?

Suspicion fell immediately on the executive branch of the government, particularly on Suarez himself, who was innocent.

From that moment on there was a flood of events. I searched for the latest Carrillo assassinations.

There were only two: in both instances he had been gunned down, once as he was strolling in the middle of the street only hours before the Communist Party became legal, and the other time when he made his first public appearance. The consequences of the two assassinations were, in both cases, much less serious than this one.

This time, the authorities asked for calm in vain. The Bunker demanded immediate explanations and Suarez's instant removal from office, which the king was forced to agree to only a few days later.

Meanwhile, the Communist Party took to the streets. The previous month, faced with the Atocha Street lawyers' murders, the Spanish Communist Party had shown some savoir faire by leading silent protests, but back then they had Carrillo as their guide and trusted the democratization process, if only minimally.

Now Carrillo was no more and nobody trusted the government.

From the short list they presented to the king, the Francoists forced the election of a harsh president who ordered a charge on the protesters. Civilians were confronting the police all around the country.

Gradually, other democratic forces began to join the demonstrations. The democratization process had been definitely lost, but the worst was yet to come.

A week later there is a coup d'etat. The king loses all his effective powers and a state of emergency is declared throughout the country. Nobody respects it. The clashes continue, and it soon becomes clear that Spain is immersed in another civil war: what no one wanted, what everyone would have liked to avoid. Cataluna and the Basque Country take advantage of the confusion to declare themselves independent, Morocco occupies the Canary Islands, invoking its sovereignty, but at least the Canary Islanders escape the worst of the war. Barcelona is besieged and completely razed. Nobody knows how many sides are involved in the fighting. In the capitals, snipers shoot at anything that moves, and a stunned international community witnesses a civil war in Europe. Spain in 1997 was what Yugoslavia was in the 1990s: a land of mass murders, exterminations, rapes, war crimes...

All types of weapons are used, biological, chemical...millions of people die, even more when a nuclear explosion destroys Madrid. Nobody knows who has detonated the device or where it has come from, everyone points fingers at each other. That proves to be too much. United Nations forces occupy Spain and impose a precarious peace. After five years of fighting, the country is ruined, destroyed, devastated, having lost almost one-third of its population, with refugees and survivors who hardly haveanything to eat. There is no parliament anymore, there is no monarchy-the royal family died with Madrid-there is nothing worth fighting for. The wounds will take time to heal. Reconstruction will take years, and no one knows how long it will last. Its echoes still resound in 2032.

I must admit that as a terrorist plan it was a very good one, better than most. I've seen them in all colors. Sometimes they prolong Franco's life and that delays the whole democratic process. In some versions, democracy arrives with Franco still alive and in command of the army. On other occasions, they avoid the death of Carrero Blanco, who becomes president of the king's first government and manages to stop the opening-up process. Others also plot to assassinate the king and create a republic. And at times they conspire for Juan Carlos not to succeed Franco; his place is then filled by another candidate to the throne, one who continues the dictator's work. But as far as number of effects per minimal cause is concerned, nothing matched this case. Who could imagine that the murder of one man in circumstances that later would be recorded as only a historical footnote could have such huge consequences?

Causing a change in history after 2012 would not have the slightest consequence; such a thing would simply make a new version of history that would coexist with those already in existence and with those constantly produced by quantum mechanics. But TT prohibits the simultaneous existence of more than one history before 7 August 2012. Thus, the preexisting history gets replaced by the one resulting from the change. Many times I've asked myself why we insist on correcting history; after all, who cares? The only answer I have been able to find is that history just as it was, good or bad, happy or unfortunate, is ours and nobody has the right to manipulate it according to who-knows-what murky interests.

All that aside, once the junction point has been located, we must fix it. This is the most delicate moment. Normally the true instigators don't expose themselves directly; they hire the necessary personnel to carry out the action and they, in turn, subcontract other menials wherever they want to intervene. So in general all we find are some poor devils who barely know anything. On the other hand, we have the names of those highly specialized in temporal jumps, who need to be apprehended. We try to scare the former to death so that they don't become repeat offenders, but we can't do much more. The latter are very difficult to surprise. They, like us, have all the time in the world at their disposal, and we do not have the necessary equipment to invest in costly and lengthy field research. Therefore, when we run into them, more out of luck than anything else, we aren't usually very considerate.

We took the tube and went to the Transition chamber. That period is visited so often it occupies a whole wing of the main basement. Wardrobe and props are stored there; likewise our weapons, disguised as everyday objects in that time period. We use those clothes so much we need to replace them quite often.

We changed for the time period and the season. We left and got in the tube again. We passed new security controls, even stricter ones, and arrived at the underground dome where the portal is kept.

When one visits it as often as we do, it ends up losing all its charm; it becomes one more piece of the armored dome's surrealist decoration.

The structure is a type of cube. It's really taller than it is wide and it isn't solid-it consists only of the lines that form the structure. It's called the Visser Portal and is made of negative mass. When you get close you start to feel a strange repulsion, because instead of attracting matter, negative mass repels it.

Therefore, it's impossible to touch it, but that isn't necessary. The structure is about five meters wide and we all fit in perfectly.

The portal is completely inactive as is. To make the trip one has to find an adequate quantum wormhole, one that connects our time period in a natural way with the temporal point we want to travel to. It seems that, at a sufficiently small scale, the space-time is not a plane but a foam where anomalous structures are constantly being formed. Some of these structures are tunnels that connect two separate regions-for example, a point from 2032 with another one in 1977. Those structures are formed and destroyed so many times that we don't have to wait very long to find the right one. When we do, the technicians feed it with energy in order to make it grow to macroscopic size, big enough so that we can cross it. But it isn't safe yet, the negative mass structures need to be attached to the Visser Portal so they become stable. First the one next to us is connected, then a similar one, a little smaller, is sent through thetunnel so that the other end is also stabilized. At that moment, if the worm-hole's chosen longitude is small enough, one can go across almost instantaneously. You simply see the image from the other side, take one step and there you are.

Before 2012 they knew that such a thing was possible, but they believed the necessary energies were so great that no government on Earth, not even all of them together, would have been able to provide the energy required to open a portal. Besides, the portals must be huge, about five kilometers in diameter, in order to guarantee a successful crossing and, in that case, we were talking about several times the mass of the sun. TT changed all that. All of a sudden, minimal quantities of energy could be used to expand a tunnel between two regions of the space-time continuum or between two different space-times.

The technicians were now prepared for the jump. Located in a control room above was our support team, in case we needed additional information or in the event there were any last-minute changes in the continuum.

"Everyone ready?" Isabel asked. As the veteran of the group, it fell to her to be the leader.

Everybody checked the equipment they carried. We'd put on those clothes so many times, we no longer noticed how strange we looked. With a bit of luck we wouldn't have to go undetected for long; if everything went as planned, it would be a simple in-and-out job. Everyone seemed to have the equipment in order. Rudy was the last one to finish. He was looking at his wrist as if one of the readings didn't quite convince him. Finally he lowered it and said yes.

"All set," he said.

Good, that was it. Now or never, as always. Marisa, the daring one, was the first one to approach the portal. She stood right at the edge. She must have been feeling all the tension. The structure's negative mass combines with the positive mass of the tunnel, and that's why the sum could have either a negative, a positive, or a null net mass. The technicians always hope to get a null mass, but they're satisfied if the combined mass isn't too big in absolute terms. That way, in theory, you shouldn't feel anything when you approach, but in reality, the negative mass is closer to your body than the tunnel is, and it's normal to feel a slight pressure that pushes you forward.

Marisa disappeared and was followed by Rudy. I stopped myself at the threshold. I have never liked going through the portal. Our tunnels are normally less than twenty centimeters long, so that it's just a matter of taking one step to cross it. However, they're long enough so that you feel the peculiar effects caused by their geometry. If you look briefly toward the tunnel's wall, you will see your own image there, being repeated ad infinitum. Of course, at the other end you see the outside landscape, but that's exactly what makes it more disconcerting.

I turned to Isabel and kissed her on the lips.

"Good luck," I said.

"Good luck," she said back. She glanced at me for a moment but then looked away and approached the tunnel as well.

Each time I cross the portal old memories of how I was recruited for the TIC come to mind.

I remember mixed emotions, nostalgia and innocence, just like when someone watches a stale disk of images and movies. Everything has that blurry patina that makes defects disappear and makes you believe those times were better than they really were.

Once a week after class I used to join my friends at the La Granja Park to chat, work out, and, eventually, spend the night partying. That spring day they had canceled my historical perspective class and I arrived earlier than usual, something that of course was part of the plan.

Wearing my shorts and a pair of red shoes Isabel would later tell me were horrible, I laid down on the grass to kill time. Some things never change, and it seems my bad taste in clothes is quite known.

She approached me. It was Isabel, of course, but I didn't know that yet. She sat down next to me, close enough so as to make sure her presence was noticed, but not so close that I thought she was after me. She was wearing the light blue dress I liked so much, the one I had given her as a present. Her hair was down and she wore almost no make-up, very natural. Everything carefully thought out, everything researched. Is there anything we haven't analyzed? She had a copy of History Reviews, a journal I wasin the habit of reading. I stared at her while she did her best to keep her eyes glued to the page.

Suddenly, she lifted her face, saw me, smiled, and buried her face in the journal again.

I got up and approached her.

"Have you read Martinson's article on Carthage?" I asked her. "The one that says it didn't really exist, that the Romans built it so they could later say they had destroyed it?"

She kept silent and still while looking at me for seconds that seemed an eternity. Her expressive eyes suggested more than I needed to know and more than she wanted to display. Something about her, something indefinable, seduced me right then; it was as if a shiver ran up and down my body. I suppose at that moment she was already playing with me.

"Well, excuse me for approaching you like this," I continued. "I saw the journal you're reading and it just so happens to be my specialty. My name's Mikel, and I teach at Logrono's UniCentral."

I shifted my body trying not to look too ridiculous. I decided to sit down next to her.

"Hi," she said, a little doubtful. "I'm Isabel. I've read the article..." She paused while her lips outlined a hint of a smile. "To tell you the truth, I think it's totally moronic."

I was completely taken aback. I was expecting many replies, but not that one. She sat there, looking at me, calm, serene, waiting. It was obviously a provocation, and it took me a while to realize it.

"Don't listen to me," she said with an open smile. "I had a bad day yesterday, that's all. Now I'm trying to put the pieces back together."

I had lost the initiative. The feeling that overcomes you at times like these is one of impotence, of being left out of the game. The problem is I still didn't know that from the moment she had appeared we were playing with marked cards.

"Although...we could discuss the subject," she added without giving me time to even think of an answer. "I warn you that I'm not easy to convince."

Her voice sounded much better this time. Later I knew why: it had been a shock for her to see me, to hear me again.

"Me either," I said regaining my control somewhat.

We got up and started walking. I didn't know that from that day on I'd never see my friends again.

Of course we didn't talk about Martinson, or Carthage, or anything like that, nor did we need to. We chatted about trivialities, work, and dreams. Isabel let her true mission be lost in a limbo of gestures and anecdotes. We wandered aimlessly from here to there, we had dinner at some strange but quiet place, we ended up in my apartment.

It was at five in the morning, after having made love for the second time, that she told me. She gave me the same old speech. Why pretend? I would find out sooner or later. One needs to have a great capacity to absorb what they tell you and I admit I didn't understand it too well. What was all that about time travel, changes in history and parallel universes? She told me as well that she had been in love with me for years although, according to my own temporal experience, we'd only met that morning. I fell back asleep from shock and the peace that comes from not understanding.

I woke up first, got up, and walked toward the window; I needed to think. Outside, one of those blue days that predicts the arrival of the heat blinded me with its light.

She stirred in bed, looking for me.

"What are you thinking about?" she asked with eyes closed. She knew I was there. She knew what I was thinking, what my doubts were.

I had been meditating. The terrible reality of what she had told me had been settling in my mind, and a question was steadily buzzing about my brain.

"Do I have any option that isn't joining the TIC ?" I asked her, in a somewhat sad voice.

"Of course," she answered me. "You may stay here."

"Is that what you want?"

Isabel didn't lie to me. She knew I needed her to be sincere, or at least to appear to be.

"No."

"What's our future like?"

Her answer was a nail in the coffin of my hopes. Her tone, however, gave her away. "We don't have any future," she said.

I didn't get all the implications of her answer. Even now I discover new sides to her short but intense response.

We had lunch together that day, we went for a walk, chatted, tried to be as honest as possible. I was sincere; she only needed to be persuasive. The portal appeared in the afternoon and I crossed it for the first time to go to the TIC. We arrived seconds after Isabel left to look for me. I went through the formalities of recruitment. It was confusing to realize everybody knew me and was happy to see me again. It was as if I had always been there, and in a sense that was true. My old colleagues greeted me and took me to the accelerated instruction booths. That was the day my life started again.

We were near the place and it was still early. Everything seemed calm; it was sunny and warm for February. What we were really hoping for was to see the unsuspecting bombers appear. Usually that's the best way to go: the meeting was so secret that there were no security devices. Who would trust a police force inherited from the Francoist system?

Each one of us had a preassigned mission, so we all knew what we had to do. We headed toward the action point.

"I think they're coming," announced Marisa, who was watching the road.

"Rudy, be on the outlook for any Extras," said Isabel, and added: "Marisa, cut them off from behind.

Mikel, you're with me. We'll use stunners as defense. That will be enough."

We're always afraid some Extra may show up, some stranger from the future, that is. Someone who'd come to ruin the plan. It's a bit dumb, but it works sometimes. So the best thing to do is not to lower one's guard.

We've studied terrorist bomb attacks so well that we can almost fix them with our eyes closed. It's a matter of blocking their way naturally, while we prepare our stunners. Normally we don't want to kill anybody, only stop the attempt. If any Extra appeared, of course, we wouldn't hesitate to kill him.

The van was approaching. They were calm. The place they had chosen for the bombing was still a few kilometers away. There were three of them, young, probably recruited in some Madrid neighborhood like Tresaguas or Horcasitas. I almost pitied them.

When they had almost reached us Isabel sent us the signal to begin. The moves were balletlike.

Somehow I seemed to be flying above the place, supervising the operation. I saw myself moving, Isabel stopping them and me stunning the first one, Isabel the second one, me the third, seizing the bomb.

Marisa was behind us observing, on guard. Rudy was a bit further out, checking out everything around us. He has something special that makes him sensitive, a sixth sense that allows him to anticipate danger.

I looked at the device; it was a common bomb, powerful enough to reach its target. Incredibly crude.

I looked it over twice. Simple, I corrected myself, like the operation, and that was something I didn't like. I looked to Rudy for a sign, but he was still calm, so I tried to relax.

Only a few seconds had gone by and everything was over.

The simplest thing was left to do, but it was the trickiest: all those people need to be moved away from there, the road needs to be cleared for Carrillo, the bomb must disappear and those men need to forget the affair. Nobody must find out.