Chris was staring at the cell phone with laserlike focus.

"Do you have any idea what it could be?" Alex asked.

"What I'm thinking," said Kaiser, "is that after Dr. Tarver smacked Rusk in the head a few times with that putter, Rusk's last conscious thought was to get revenge on the bastard if he could. He couldn't use the telephone, but he could move his foot enough to write in the blood on the floor."

"A's number twenty-three!" Alex cried.

"Exactly. But Neville and I have googled our way through all the baseball rosters of the Oakland A's for the past hundred and six years. We've tried every player we can find who wore number twenty-three, but no combination of any of their names or birthdays or batting averages or anything else is the password."

Alex thought furiously. "You're making an assumption that A's refers to the baseball team. Throw that out and start from zero. A's number…What else could it mean?"

"The only hits that search engines kick up are baseball-related. I just put in a call to the NSA in Washington. They've put it in the queue for a supercomputer."

"It can't be that hard," said Alex. "It's something Rusk thought we could figure out. What were his other passwords?"

"One was pi to the ninth decimal place."

"Pi," Alex echoed.

"A couple were names from classical literature. One was the speed of light."

In a strangely detached voice, Chris said, "How did he write 'miles per second squared'?"

"Who's that talking?" asked Kaiser.

"Chris," Alex replied. "Can you answer his question?"

"Hang on."

Alex looked down. Chris had taken hold of her elbow. "The only A's number I know about is Avogadro's number," he said.

"What's that?"

"A constant in chemistry. It has to do with molar concentration. Every high school chemistry student has to memorize it."

"What was that?" asked Kaiser.

"Chris has got a password for you to try. Hold on." She looked at Chris. "What's the number exactly?"

"Six-point-oh-two-two times ten to the twenty-third power."

"The twenty-third power?" Alex echoed.

Chris nodded.

"That's the twenty-three? A's number twenty-three."

"How would you type all that out?" asked Kaiser.

Chris looked up at the ceiling. "Six period zero two two X one zero two three."

"I heard him," said Kaiser. "Neville's typing it in."

Alex's ears roared as she waited.

"No dice," said Kaiser, obviously deflated. "That's not it."

Alex closed her eyes.

"Try leaving out the decimal," said Chris.

"All right," said Kaiser. "Byrd's trying it-"

Alex winced as a scream of triumph came through the phone.

"That's it!" shouted Kaiser. "We're in!"

Alex was squeezing the phone so tightly that her hand hurt. "What does it say? What's in the file, John?"

"Hang on. My God…it's a confession, all right. There's pages and pages of it."

Alex caught Chris's hand in hers. "Do you see Grace's name? Tell me you see Grace's name."

"I'm looking…I see several of the victims you listed for me."

Alex's whole body was shaking. Chris's jaw muscles were working steadily.

"I see it," Kaiser murmured. "Grace Fennell. I'm reading it right off the page."

Alex felt tears streaming down her cheeks. The lump in her throat kept her from speaking until she managed to swallow. "Copy that file now, John."

"Neville already copied it," he assured her. "He's printing it out right now."

"What about Thora?" Chris asked. "Or anything about me?"

"It's probably the last entry in the file," Alex said.

"No. The last entry is a guy named Barnett. An oilman. Rusk thinks Barnett is going to approach him any day about getting a divorce."

"Keep looking."

"I am. Wait…here it is, Christopher Shepard, MD. It's all here, Alex. All the proof in the world."

Chris was holding his fist over his mouth, as though he might lose control of himself.

"I've never seen anything like this," Kaiser said in a fascinated voice. "I mean, I've discovered the trophies of serial murderers…monsters, aberrations…but this is just business. Naked fucking greed, by people who knew better."

Alex saw tears in Chris's eyes.

"Listen to this," said Kaiser. "'In November of 1998, I was approached by a law school classmate named Michael Collins, a criminal lawyer who works for Gage, Taft, and LeBlanc. Collins wanted my advice about a client, a physician named Eldon Tarver. Dr. Tarver's wife had recently died of cancer, but his wife's family believed she was the victim of foul play. They were a wealthy family, and Tarver feared they had gotten the police involved. He'd hired Collins because he believed he was in danger of being arrested. I was puzzled that Collins would seek out my help, because I specialize in divorce, but Michael told me that he needed my psychological insight, not legal expertise.

"'Over the course of two interviews with Dr. Tarver, I realized the nature of Michael's problem. His client was guilty. Tarver didn't come right out and state this fact, but it was plain to me. I had never encountered such arrogant self-assurance in my life, not even from my father, and that's saying a lot. In the end, no charges were brought against Dr. Tarver, mainly because no forensic evidence of murder could be produced, despite two separate autopsies, one by a renowned pathologist. In fact, the second autopsy was what convinced the police that no murder had in fact occurred. But I knew different.'

"Do you want me to go on?" Kaiser asked.

Alex looked at Chris, whose eyes were closed. "Do you want me to turn off the speaker?"

"No."

"Go ahead, John."

"'I had no further contact with Dr. Tarver until almost two years later, when I encountered him during a weekend hunting trip at the Chickamauga Hunting Camp. During that weekend, I found myself alone with him for an extended period. He asked several forward questions about my divorce practice, questions that I took to be a strange sort of overture. Strangely sure that I could trust Tarver, I decided to step out on a limb. I remarked that, after years of experience in my field, I had come to believe that in certain cases involving wealthy clients, a timely death would be a preferable alternative to divorce. Dr. Tarver's response was instantaneous: "I think you mean an untimely death, don't you?"

"'That was the beginning of our partnership. Under the influence of a moderate amount of alcohol, Dr. Tarver assured me that he could kill anyone without leaving a forensic trace. He looked on this, he said, as a sort of professional challenge and claimed that every pathologist had at some point in his life had thoughts along those lines. It was only natural, he said.

"'Before we left Chickamauga that weekend, the basics of our plan had been worked out. I had wealthy clients coming to my office every week, begging me to spare them a huge settlement and get them more time with their children. I could judge which clients had sufficient hatred and anger to consider actually eliminating their spouses. Dr. Tarver and I would have as little contact as possible. After securing a go-order from a client, I would initiate contact by sending a false spam message to one of his e-mail accounts. The next day I would park my car at the Annandale Golf Club and play eighteen holes of golf. There would be a large packet in my trunk when I arrived. When I left, the packet would be gone. That packet contained everything about the intended victim, and all of it supplied by the victim's spouse: medical history, daily schedule, car keys, house keys, vacation plans, security codes, e-mail passwords, everything. That was the only "contact" Tarver and I ever had, and even that involved no face-to-face interaction. It could never be proved or traced because Dr. Tarver wasn't a member of that club. He had a friend who played golf there almost every day, and Tarver could go as a guest whenever he chose. He opened the trunk with a key I gave him that first weekend at Chickamauga. I have only spoken to Dr. Tarver a few times in the past five years, and those times by pure happenstance. But together, he and I have murdered nineteen people.'"