Maybe Sandy's right. The thought hit him with the force of a hammer. Maybe, just maybe, there is a way back for me.

He put the vodka back on the bar. Turning on his heels, he started to walk through the doors, and out into the cold, dark streets. The chords of 'Someone Saved My Life Tonight' were crashing through the pub as Sky News flashed up a picture of Katie Dartmouth and faded into the ads.

Just for once, Elton, thought Porter with a wry smile, you might be right.

FOUR.

The river looked better in the morning, Porter thought. The tide was high, and the water was lapping right up close to the barricades. A couple of tourist boats were heading down towards Greenwich for their first run of the day. Sunshine was breaking out across Battersea Park, sending shafts of brilliant light skimming out across the water. Hell, we all look better at dawn, Porter told himself. The day is still fresh, and we can still hope.

He glanced up at the headquarters of the Firm, right next to Vauxhall Bridge. He'd walked past it a thousand times during the few years he'd dossed down in the area. Until he saw Sandy again, and realised how much she'd missed him, it had never occurred to him to go inside.

I thought my soldiering days were buried. Until now.

Porter checked himself in the reflection from a phone box. Not so bad, he decided. After leaving the pub, he'd found a quiet spot close to the bus depot, and bedded himself down among some tossed-out cardboard boxes. He hadn't slept well, but then he never did. At five in the morning, he'd walked a mile down to the Asda superstore on the road that snaked towards Brixton. The place was open all night, it was as cheap as dirt, and they didn't mind what the customers looked like. Porter picked himself out a new pair of jeans, a white shirt, some socks and trainers, and a sweater. The whole outfit came to thirty quid. He slipped into the toilets, washed himself as best he could in the sink, then put on the new clothes. He tossed the old ones into the bins outside, then went to the cafe and blew another fiver on a full English breakfast, and a jug of coffee. The water, at least, was free. By the time he'd finished that, he felt almost like a human being again.

He glanced one more time at the Firm. The office was deliberately forbidding: a mass of turrets and spikes, with a huge inner courtyard. There were a dozen armed and uniformed police officers at the entrance, and no doubt twice as many plain-clothes men keeping an eye on it as well. There was no building in London more heavily guarded. Don't worry about it, Porter told himself. You can do this. It's just a matter of holding your nerve.

He walked steadily towards the building, at an even, unvarying pace. Run into this place and they were likely to gun you down. Looking across the river to the clock on Big Ben, he noted that it was just after seven in the morning. Early. But the spooks never slept. And certainly not when they were in the middle of a crisis.

The policemen looked at him suspiciously as he walked across the driveway, and into the entrance lobby, but they made no attempt to stop him. It's a public building, Porter reflected. They have to at least let people walk into the place. It was only once you checked in at the desks that they ran you over for guns and knives.

The foyer was decorated in grey, with slate floors, and a bank of glass at the front. Marble-clad walls led up to a bank of elevators. Along one side there was a reception desk with three uniformed guards sitting at it. At the other, there was a pair of black leather sofas, and a collection of the day's papers spread out on a coffee table. All of them, Porter noticed, had pictures of Katie Dartmouth on them. 'BRING OUR BOYS HOME TODAY' said huge letters across the front page of the Independent Independent. 'SAVE HER' said the Mirror Mirror.

Porter walked steadily up to the desk. A thickset man in his forties looked straight at him, his expression as welcoming as a chunk of granite.

'I know how to get Katie Dartmouth out,' said Porter.

Even as he delivered the sentence, Porter knew how ridiculous he sounded. If it wasn't for the fact he knew it was true, he'd be laughing at himself.

The receptionist looked at him, taking half a second to make a judgement, and then reached underneath his desk to press a button. Even though he was trained to remain impassive, Porter could tell he had already reached his own verdict. He thinks I'm a nutter. Who know, maybe he's right?

Five armed officers appeared from the door that led away from the elevators. They walked quickly across the slate floor. Not running, but moving with purpose. A few people were coming through the entrance doors, heading towards the lifts to get to their desks, but they simply made way for the armed men, paying them no attention. 'We'll have to ask you to leave, sir,' said the first officer, standing in front of Porter.

He glanced at the man's face. It was expressionless, like rock. He was wearing no uniform but he didn't need to. There was an MP-5 assault rifle strapped to his chest, and that gave him all the authority he needed.

Porter looked straight into his steely blue eyes. 'I know how to get Katie Dartmouth out.'

He could see the man's reaction in his face. Nutter, he was thinking. Just like the other guy. But he remained silent.

'I can get her out.'

'This way, please, sir,' said the officer.

Porter could feel his chest thumping. This was his one chance to show Sandy he could amount to something. To look her in the eye without feeling ashamed of himself. He'd no more throw it away than he'd throw away his own life.

'I'm the only man who can get through to her kidnappers,' Porter shouted.

He could see a few of the office workers looking at him distastefully before hurrying on. None of them wanted to hear what he was saying, and none of them were looking in his direction. The five guards were slowly closing in on him, forming a tight semicircle from which there was no chance of escape.

'This is your one chance to save her,' said Porter. 'I was SAS, I know something about the man who's holding her, something we can use.'

He could feel a hand grabbing hold of his arm. The MP-5 wasn't jabbing into his chest, but it was definitely pointed in his direction, and the expression of the man with his finger on the trigger suggested he wouldn't hesitate to use it if he had to. They were starting to move him towards the door. Porter shrugged himself free. These goons weren't going to listen to anyone, he reflected bitterly. Osama bin Laden could walk through the door offering to turn himself in, and they'd tell him to come back when he'd made an appointment. 'I can walk,' he growled.

A fresh blast of cold air struck Porter in the face, as he stepped out into the morning air. A gust of wind was blowing through him. It can take my hopes and blow them away, Porter told himself. I must have been mad to think they would listen to me.

'Don't come back,' said the officer firmly.

A Jaguar was pulling up outside, and a man in a charcoal-grey suit was climbing out of the back seat. Porter recognised him at once. Sir Angus Clayton, the director general of the Firm. Porter had seen his picture in the papers he sometimes fished out of the bins he slept next to. He might even have used his mugshot as a blanket once or twice. A tall man, with a fast-disappearing head of black hair, and a face that was shallow and drawn, he looked tired even though he hadn't started work yet. Porter was standing only a few yards away from him. If I don't take this chance, he told himself, then I'll never get another.

'I can get Katie Dartmouth out for you, Sir Angus,' he shouted.

The man looked at him. His eyes were focused, intent, as the words struck home. He was assessing Porter in an instant, scanning his face, using a lifetime of experience in the intelligence trade to make a snap judgement on whether the man might be worth listening to. He slammed the door shut on the Jaguar, and started walking towards the entrance doorway.

The guard was tightening his grip on Porter's arm. 'We've already asked you to leave, sir,' he snapped.

Porter took a step forward. 'One minute of your time,' he said. 'That's all I'm asking for.'

Sir Angus kept walking towards the revolving glass door that led into the Firm's headquarters. From the expression on his face, you couldn't even tell if he had heard Porter.

'If you make any more trouble, sir ' started the guard.

Porter shrugged him aside.

'That woman is going to die in five days' time, Sir Angus,' said Porter. 'And I'm the only man who can do anything about it.'

The guard was tugging him back.

'One bloody minute. I'm SAS, I'm '

'Sir, you are risking arrest,' the guard said.

Sir Angus paused. His hand was already pushing the revolving door open, but his feet had stopped moving. Slowly, he turned round. His eyes were looking straight at Porter, questioning and probing at the same time. 'You're Regiment?'

Porter nodded.

'What was the code name of the Firm's liaison officer in Hereford in 1990?'

'Zebra, sir,' replied Porter, without a flicker of hesitation.

'And do you keep in touch with Jim West?'

'Not likely, sir,' replied Porter. 'The bloke died on a black op in Somalia.'

I've passed the test, thought Porter. Only a Regiment man could answer those questions.

'A minute is too long,' said Sir Angus quietly. 'I'll give you thirty seconds.'

The guard let go of Porter, but he was still standing just a couple of feet behind him, and his gun was still cocked, ready to drop him if he created any trouble. Porter paused. Thirty seconds, he told himself. Better make this good.

'In 1989, I was in the SAS,' he said, his tone confident and strong. 'There was a hostage-rescue mission in Beirut. A guy called Kenneth Bratton. There was a young kid, one of the Hezbollah boys. I spared his life. It's that Hassad bloke, the one who is holding Katie Dartmouth hostage. I recognised him because of the deformed mouth.' Porter paused, looking straight into Sir Angus's eyes. He could tell he'd caught his interest: whether he'd convinced him or not it was impossible to say. 'He'll talk to me, because he owes me,' he continued. 'I know it might not work, but it's worth a try, and what else have you got? If you've got a secure line to him, tell him there's an SAS guy with two fingers missing on his left hand. Tell him I want to come and talk to him.'

Sir Angus glanced down at Porter's left hand. He could see at once the two stumps where his fingers used to be. He rubbed his brow as his face creased up into a frown.

Porter could feel his heart thumping against the walls of his chest. 'I'm on the level,' he said. 'I was Regiment. You can check my records.'

Sir Angus hesitated. 'Here's what I'm going to do,' he said. He nodded towards the guards. 'These gentlemen are going to take you to a secure room. A case officer is going to come down and check out your story.'

'Thank you, sir,' said Porter.

'But let me tell you my terms,' Sir Angus continued. He was already starting to turn back to the revolving door. 'If you're wasting our time, I'm going to get them to beat the bloody hell out of you, then take you to the back of this building, and feed you to the sodding fish. Got that? You can leave now if you want '

'I'll take those terms,' said Porter with quiet determination.

FIVE.

On the table in front of him, there was jug of coffee and a plate of biscuits. Porter took the jug, and poured himself a third cup of coffee, drinking it down in a couple of gulps, then eating another of the biscuits. He'd have polished off the whole plate in the next few minutes, he realised. When you lived on the streets, you ate your food quick, before someone stole it, the same way a wild dog does.

He'd been sitting here for ten or fifteen minutes already. The guards had taken him down three flights in the elevator, into the network of cells and interrogation rooms that lay deep underneath the Firm's headquarters. They'd remained silent during the time it took to bring him here: Porter could tell the guy in charge was looking forward to roughing him up if his story didn't check out. 'Someone will be along to see you in a minute,' he had said briskly, as he ushered Porter into the room.

It didn't look like a prison cell, Porter thought, but that's what it was. The door was locked behind him, and he reckoned you'd need at least a couple of pounds of Semtex to break through it. There was grey carpet on the floor, and the walls were painted a grey-white. A simple table was in the centre of the room, with the coffee jug on it, and next to it there was a chair. A flat-screen TV nestled in one corner. Otherwise, the room was completely empty.

Porter took another biscuit, and flicked on the TV. Sky News was covering the Katie Dartmouth hostage story twenty-four hours a day now. The presenter was going over live to Downing Street, where the Prime Minister was about to make a statement. Porter watched with interest, as the familiar figure appeared on the screen. He paused, and there was catch in his throat as he concentrated on what he was about to say. 'Let me just start by saying that all our thoughts are with Katie Dartmouth and her family at this time,' he began, looking straight at the camera. 'I just say this to the people who have taken her. Whatever your quarrel is with the British government, then we can talk about that, but there is nothing to be gained from taking the life of an innocent young woman. Now, to the British people I say this. They are asking for British troops to be withdrawn from Iraq, but nothing is more important than that we stay the course, and don't turn our back on the war on terror. Sir Perry Collinson has been put in charge of our diplomatic efforts to bring Katie Dartmouth out of the Lebanon. Whatever he needs to bring that about, you may be assured it will be put at his disposal.' The PM paused, coughing slightly. 'This certainly isn't the moment for sound bites,' he continued. 'But in our darkest hours, our finest men come forward. Perry Collinson one of those men.'

Porter turned the sound down. 'Bollocks,' he muttered out loud. That tosser couldn't get a Cheesy Wotsit out of its packet. He certainly doesn't know how to get Katie Dartmouth out of a cellar in Beirut.

Porter snapped rigidly to attention as he heard the lock turn in the door. A woman was coming into the room. He guessed she was about thirty-five, with dark hair that stretched down no further than the bottom of her neck, and with clear blue eyes that were set in a solid, serious face. She was wearing a black jacket and black skirt, with a white blouse and an amber necklace hooked around her delicate white skin. Just keep yourself focused, Porter told himself. Finally show Sandy that you can do something.

'My name is Layla Thompson,' she said, looking straight at Porter. 'And you are ...?'

'Porter,' he replied crisply. 'John Porter.'

She pulled out a chair and sat down opposite him. There was a notepad and a pen in front of her, and she instinctively reached for them, but Porter noticed she wasn't writing anything down. Just drawing a series of rectangles. 'Sir Angus says you know how to get to Hassad Naimi,' she said.

'I've been through it once with the boss,' said Porter. 'I was in the SAS back in '89. We went into the Lebanon to get out a hostage. Hassad was there. He was just a kid then, so I spared his life. I recognised him from the shape of his mouth. It's deformed, you can't miss it.'

'And you think he'll talk to you?' said Layla.

She was about to pour herself a coffee and take a biscuit, but then she noticed they were all gone.

'Like I said, I let him live,' said Porter. 'Three good men died on that mission, and I lost two fingers on my left hand. I've regretted it every bloody day since, but that doesn't change the facts. He owes me. Arabs may not be good at much, and I wouldn't trust the bastard any further than I could throw a camel. But they never forget an obligation. Not when their honour is at stake.'

'Why did you let him live?'

'Christ, he was just a kid ...'

'A dangerous one, however.'

'We've been through all that,' snapped Porter. 'It's not important now.'

'Which years were you in the Regiment?' said Layla.

'From '88 to '92,' answered Porter.

Layla nodded. She had the same patient manner of a doctor, listening carefully to what you said, while neither approving or disapproving. 'Here's what I'm going to do,' she said. 'I'll take some fingerprints, and a snip of your hair, so we can run ID checks, and a DNA test. We need to make sure you are who you say you are. If that works out, then we can have a conversation. OK?'

Porter nodded. It was going to take time, he told himself. You couldn't walk back in from the cold after fourteen years and expect the security services to start trusting you.

It took only a few moments to snip a lock of hair and take an impression of his fingertips, and then Porter was alone again. Layla had left, locking the door behind her: they didn't believe him yet, he noted, but they weren't going to risk losing him either.

Porter flicked on the TV, but there were just replays of the PM's statement on Katie Dartmouth. One of the political commentators was talking about the by-election coming up in nine days' time, and how the government faced a potential humiliation if Katie was executed at the weekend. There were more calls from the Opposition for troops to be taken out of Iraq, and a vigil had already been started by the 'Stop the War' coalition in Trafalgar Square. Porter turned it off again. He'd watched enough by now to know how badly they wanted Katie out of there.

Alone with my own thoughts, he reflected. Always a dangerous place. An hour slipped by and then another. Porter could feel himself growing desperate for a drink. The coffee pot was empty, and the biscuits were all gone. As he stared at the walls, the doubts start to creep up on him, like maggots crawling across rotten meat. What the hell am I doing here? Who in the name of Christ do I think I am kidding?

I must be mad to want to get back into this, he decided, as he stood up to pace around the small room. Whatever it is a man needs to be made of to turn him into a warrior, I haven't got it. And there is no point in thinking I'm suddenly going to acquire it at my age. And there is no point in thinking I'm suddenly going to acquire it at my age.

He looked at the door again. If only it wasn't locked, he'd just walk straight out of here. Get back to his archway, use his spare cash to buy a couple of bottles of vodka, and get some rest. If they don't come back soon, I'm going to start banging on the door. I can't deal with this much longer. Not without something to drink.

Just then the door started to open. Layla walked in. 'OK, so you are who you say you are,' she said, sitting down behind the table.

She motioned to Porter to sit down opposite her, but he preferred to stand.

'The problem is, John Porter is a fuck-up,' she continued.

Layla glanced down at a sheaf of computer printouts she'd been carrying under her arm. 'We've retrieved your records. And indeed, you were in the SAS from 1988 to 1992. But, how shall I put this delicately, you weren't exactly gunning for any medals, were you?'

'I was good enough to get in,' growled Porter.

'But not good enough to stay in,' said Layla, her tone laced with sarcasm. 'You fucked up in the Regiment. You were sent off to be a range warden but you couldn't handle that either. After you left the army, you tried a few jobs, but you couldn't hold them down. Your wife kicked you out more than ten years ago. She divorced you five years ago but you probably didn't even know because her lawyers didn't have anywhere to send the papers.'

She shrugged, flicking a piece of dust off the shoulder pad of her black jacket. Porter watched it fall to the floor: he knew how it felt.

'If I may put it this way, John Porter isn't exactly the first person the nation would turn to in its hour of need.'

Porter stared at the floor. I shouldn't have bothered, he was telling himself. I should have just gone somewhere I could get a drink.

'I shouldn't have come ...'