The day had drained me, as if a greedy, dark force had sucked the light right out of my being. I felt the invasive hands of a prison guard named Helen, and smelled the stale stench of hovels that once had housed remorseless, hateful men. I remembered holding slides up to lamplight in a hotel bar in New Orleans at the American Academy of Forensic Sciencesa annual meeting. Robyn Naismithas homicide was then unsolved, and to discuss what had been done to her as Mardi Gras revelers loudly drifted past had somehow seemed ghastly.

She had been beaten and bullied, and stabbed to death, it was believed, in her living room. But it was Waddellas postmortem acts that had shocked people most, his uncommon and creepy ritual. After she was dead, he undressed her. If he raped her, there was no evidence of it. His preference, it seemed, was to bite and repeatedly penetrate the fleshier parts of her body with a knife. When her friend from work stopped by to check on her, she found Robynas battered body propped against the television, head drooping forward, arms by her sides, legs straight out, and clothing piled nearby. She looked like a b.l.o.o.d.y, life-size doll returned to its place after a session of make-believe and play that had turned into a horror.

The court testimony of a psychiatrist was that after Waddell had murdered her, he was overcome by remorse and had sat talking to her body for perhaps hours. A forensic psychologist for the Commonwealth speculated quite the opposite, that Waddell knew Robyn was a television personality and his act of propping her body against the television set was symbolic. He was watching her on TV again and fantasizing. He was returning her to the medium that had brought about their introduction, and this, of course, implied premeditation. The nuances and twists in the endless a.n.a.lyses got only more complicated with time.

The grotesque display of that twenty-seven-Year-old anchorwomanas body was Waddellas special signature. Now a little boy was dead ten years later and someone had signed his work - on the eve of Waddellas execution - the same way.

I made coffee, poured it into a thermos, and carried it into my study. Sitting at my desk, I booted up my computer and dialed into the one downtown. I had yet to see the printout of the search Margaret had conducted for me, though I suspected it was one of the reports in the depressingly large stack of paperwork that had been in my box late Friday afternoon. The output file, however, would still be on the hard disk.

At the UNIX log-in I typed my user name and pa.s.sword and was greeted by the flashing word mail. Margaret, my computer a.n.a.lyst, had sent me a message.

"Check flesh file," it read "Thatas really awful," I muttered, as if Margaret could hear.

Changing to the directory called Chief, where Margaret routinely directed output and copied files I had requested, I brought up the file she had named Flesh.

It was quite large because Margaret had selected from all manners of death and then merged the data with what she had generated from the Trauma Registry. Unsurprisingly, most of the cases the computer had picked up were accidents in which limbs and tissue had been lost in vehicular crashes and misadventures with machines. Four cases were homicides in which the bodies bore bite marks. Two of those victims had been stabbed, the other two strangled. One of the victims was an adult male, two were adult females, and one was a female only six years old. I jotted down case numbers and ICD-9 codes.

Next I began scanning screen after screen of the Trauma Registryas records of victims who had survived long enough to be admitted to a hospital. I expected the information to be a problem, and it was. Hospitals released patient data only after it had been as sterilized and depersonalized as operating rooms. For purposes of confidentiality, names. Social Security numbers, and other identifiers were stripped away. There was no common link as the person traveled through the paperwork labyrinth of rescue squads, emergency rooms, various police departments, and other agencies. The sorry end of the story was that data about a victim might reside in six different agency data bases and never be matched, especially if there had been any entry errors along the way. It was possible, therefore, for me to discover a case that aroused my interest without having much hope of figuring out who the patient was or if he or she had eventually died.

Making a note of Trauma Registry records that might prove interesting, I exited the file. Finally, I ran a list command to see what old data reports, memos, or notes in my directory I could remove to free up s.p.a.ce on the hard disk. That was when I spotted a file I did not understand.

The name of it was tty07. It was only sixteen bytes in size and the date and time were December 16, this past Thursday, at 4:26 in the afternoon. The fileas contents was one alarming sentence: I canat find it.

Reaching for the phone, I started to call Margaret at home and then stopped. The directory Chief and its files were secure. Though anyone could change to my directory, unless he logged in with my user name and pa.s.sword, he should not be able to list the files in Chief or read them. Margaret should be the only person besides me who knew my pa.s.sword. If she had gone into my directory, what was it she could not find and who was she saying this to? Margaret wouldnat, I thought, staring intensely at that one brief sentence on the screen.

Yet I was unsure, and I thought of my niece. Perhaps Lucy knew UNDO. I glanced at my watch. It was past eight on a Sat.u.r.day night and in a way I was going to be heartbroken if I found Lucy at home. She should be out on a date or with friends. She wasnat.

"Hi, Aunt Kay." She sounded surprised, reminding me that I had not called in a while.

"Howas my favorite niece?"

"Iam your only niece. Iam fine."

"What are you doing at home on a Sat.u.r.day night?" I asked.

"Finishing a term paper. What are you doing at home on a Sat.u.r.day night?"

For an instant, I did not know what to say. My seventeen-year-old niece was more adept at putting me in my place than anyone I knew.

"Iam mulling over a computer problem," I finally said.

"Then youave certainty called the right department," said Lucy, who was not given to fits of modesty. "Hold on. Let me move these books and stuff out of the way so I can get to my keyboard."

"Itas not a PC problem," I said. "I donat guess you know anything about the operating system called UNIX, do you?"

aI wouldnat call UNIX an operating system, Aunt Kay. Itas like calling it the weather when itas really the environment, which is comprised of the weather and all the elements and the edifices. Are you using A-T ana T?"

"Good G.o.d, Lucy. I donat know."

"Well, what are you running it on?"

"An NCR mini.' "Then itas A-T ana T."

"I think someone might have broken security," I said.

"It happens. But what makes you think it?"

"I found a strange file in my directory, Lucy. My directory and its files are secure - you shouldnat be able to read anything unless you have my pa.s.sword."

"Wrong. If you have root privileges, youare the super user and can do anything you want and read anything you want."

"My computer a.n.a.lyst is the only super user."

"That may be true. But there may be a number of users who have root privileges, users you donat even know about that came with the software. We can check that easily, but first tell me about the strange file. Whatas it called and whatas in it?"

"Itas called t-t-y-oh-seven and thereas a sentence in it that reads: aI canat find it.a "I heard keys clicking.

"What are you doing?"

I asked.

"Making notes as we talk. Okay. Letas start with the obvious. A big clue is the fileas name, t-t-y-oh-seven. Thatas a device. In other words, t-t-y-oh-seven is probably somebodyas terminal in your office. Itas possible it could be a printer, but my guess is that whoever was in your directory decided to send a note to the device called t-t-y-oh-seven. But this person screwed up and instead of sending a note, he created a file."

"When you write a note, arenat you creating a file?" I puzzled.

"Not if youare just sending keystrokes."

"How?"

"Easy. Are you in UNIX now?"

"Yes."

"Type cat redirect t-t-y-q -" "Wait a minute."

"And donat worry about the slash-dev a "Lucy, slow down."

"Weare deliberately leaving out the dev directory, which is what Iam betting this person did."

"What comes after cat?"

"Okay. Cat redirect and the device "

"Please slow down."

"You should have a four-eighty-six chip in that thing, Aunt Kay. Whyas it so slow?"

"Itas not the d.a.m.n chip thatas slow!"

"Oh, Iam sorry," Lucy said sincerely. "I forgot."

Forgot what? "Back to the problem," she went on. "Iam a.s.suming you donat have a device called t-t-y-q, by the way. Where are you?"

"Iam still on cat," I said, frustrated. "Then itas redirect a d.a.m.n. Thatas the caret pointing right?"

"Yes. Now hit return and your cursor will be b.u.mped down to the next line, which is blank. Then you type the message you want echoed to t-t-y-qas screen."

"See Spot run," I typed.

"Hit return and then do a control C," Lucy said. "Now you can do an ls minus one and pipe it to p-g and youall see your file."

I simply typed -Is-and caught a flash of something flying by.

"Hereas what I think happened," Lucy resumed. "Someone was in your directory - and weall get to that in a minute. Maybe they were looking for something in your files and couldnat find whatever it was. So this person sent a message, or tried to, to the device called t-t-y-oh-seven. Only he was in a hurry, and instead of typing cat redirect slash d-e-v slash t-t-y-oh-seven, he left out the dev directory and typed cat redirect t-t-y-oh-seven. So the keystrokes werenat echoed on t-t-y-oh-sevenas screen at all. In other words, instead of sending a message to t-t-y-oh-seven, this person unwittingly created a file called t-t-y-oh-seven."

"If the person had typed in the proper command and sent the keystrokes, would the message have been saved? " I asked.

"No. The keystrokes would have appeared on t-t-yo-h-sevenas screen, and would have stayed there until the user cleared it. But you would have seen no evidence of this in your directory or anywhere else. There wouldnat be a file."

"Meaning, we donat know how many times somebody might have sent a message from my directory, saying it was-done correctly."

"Thatas right."

"How could someone have been able to read anything in my directory?" I went back to that basic question.

"Youare sure no one else might have your pa.s.sword?"

"No one but Margaret."

"Sheas your computer a.n.a.lyst?"

"Thatas right."

"She wouldnat have given it to anyone?"

"I canat imagine that she would," I said.

"Okay. You could get in without the pa.s.sword if you have root privileges," Lucy said. "Thatas the next thing weall check. Change to the etc directory and vi the file called Group and look for root group - thatas r-o-o-t-g-r-p. See which users are listed after it."

I began to type.

"What do you see?"

"Iam not there yet," I said, unable to keep the impatience out of my voice.

She repeated her instructions slowly.

"I see three log-in names in the root group," I said.

"Good. Write them down. Then colon, q, bang, and youare out of Group."

"Bang?"

I asked, mystified.

"An exclamation point. Now youave got to vi the pa.s.sword file - thatas p-a-s-s-w-d - and see if any of those log-ins with root privileges maybe donat have a pa.s.sword."

"Lucy." I took my hands off the keyboard.

"Itas easy to tell because in the second field youall see the encrypted form of the useras pa.s.sword, if he has a pa.s.sword. If thereas nothing in the second field except two colons, then heas got no pa.s.sword."

"Lucy."

"Iam sorry, Aunt Kay. Am I going too fast again?"

"Iam not a UNDO programmer. You might as well be speaking Swahili."

"You could learn. UNIX is really fun."

"Thank you, but my problem is I donat have time to learn right now. Someone broke into my directory. I keep very confidential doc.u.ments and data reports in there. Not to mention, if someone is reading my private files, what else is he looking at and who is doing it and why?"

"The who part is easy unless the violator is dialing in by modem from the outside."

"But the note was sent to someone in my office - to a device in my office."

"That doesnat mean that an insider didnat get someone from the outside to break in, Aunt Kay. Maybe the person snooping doesnat know anything about UNIX and needed help to break into your directory, so they got a programmer from the outside."

"This is serious," I said.

"It could be. If nothing else, it sounds to me like your system isnat very secure."

"Whenas your term paper due?" I asked.

"After the holidays."

"Are you finished?"

"Almost."

"When does Christmas vacation start?"

"It starts Monday."

"How would you like to come up here for a few days and help me out with this?" I asked.

"Youare kidding."

"Iam very serious. But donat expect much. I generally donat bother with much in the way of decorations. A few poinsettias and candles in the windows. Now, I will cook."