The sky was beginning to lighten. Soon, it would be five a.m., and the world would yawn to life. I realized the only way to get what I wanted from Thorpe was to use his own tactics against him. My mother had once told me that her success as a trial attorney had to do with her approach to the witness stand. Many attorneys, she said, made the mistake of beginning a cross-examination from the standpoint of the aggressor. In their eagerness to make their own case, they bullied the witness. She said she saw herself, at the outset of any cross-examination, as a negotiator. Prior to a trial, she'd find out everything she could about the witnesses, and tailor her questions to each personality. In this way she could lead the conversation in the direction she wanted it to go.

By asking me to see him again, Thorpe had opened a door.

"Let's a.s.sume for the sake of argument that it wasn't McConnell," I said. "Who else could have done it?"

Thorpe stood and began clearing the dishes. "We could walk down to Mangosteen afterward. Great little Vietnamese place. Best garlic beef in the city."

I ignored his invitation and pressed on. "You interviewed dozens of people for the book. There must have been others who stood out as possibilities."

"Have you ever had mangosteen berry juice? It's delicious."

He took the plates into the kitchen, and I followed him with the gla.s.ses and leftover pizza.

"I'm not asking you to remember offhand. You must have notes tucked away somewhere."

He put the dishes in the already-full sink, squirted some dishwashing liquid into the pile, and turned on the hot water. "We'll let them soak."

"I like Vietnamese food," I said after a pause. "I haven't had it in a while."

Thorpe turned and leaned against the counter. A few seconds pa.s.sed. "John Wheeler," he said finally. "He was a janitor at Stanford. A student claimed to see him talking to Lila in the math building the night before she died."

"I don't remember him from the book."

Thorpe shrugged. "I talked to him once. He was in the first draft, but he ended up on the cutting-room floor-he wasn't very interesting."

"Do you have any idea where I might find him?"

Thorpe shook his head. "That was forever ago. But I can probably find his old address. Come with me."

If the bedroom was the one place in Thorpe's house where neatness reigned, the garage was where he had completely abandoned any pretense of order. It was designed to hold two cars, but was so overrun with boxes, gardening tools, sports equipment, and old furniture that it would have been difficult to even fit a motorcycle in there. The garage was lit by fluorescent tubes, and in the exaggerated brightness Thorpe looked increasingly haggard in his wrinkled slacks and wine-stained sweater, his morning beard. Beneath the scent of aftershave, I detected a faint but unmistakable tinge of body odor. There was a spot in the book where he described Peter McConnell as a modern-day Jekyll and Hyde, but I thought the comparison could be more aptly applied to Thorpe himself. I had the feeling that the garage, more than any other room in the house, represented the real Thorpe-not the stylish, put-together author persona he presented to the world, but the man he was in his most private moments, ripe-smelling and uncertain amidst the detritus of his lonely life.

"Welcome to the wine cellar," he quipped.

I tripped over an old rug that was rolled up on the floor, and Thorpe took my arm to steady me. We picked our way through tottering shelves, a weight bench, and several full recycling bins to a metal file cabinet crammed into a corner. "It may look like a disaster," Thorpe said, "but believe it or not, I actually have a system. All the notes for my old books are in this cabinet, arranged top to bottom, first book first."

He opened the top drawer and began thumbing through the green hanging files, which emitted a musty, old-paper smell that made me think of a chiropractor's office where I'd temped one summer after college. The temp job lasted an interminable three weeks. Just days after I left, a disgruntled former patient had walked in and shot up the office, killing the chiropractor and critically injuring the receptionist, for whom I had been the replacement while she was on her honeymoon. The event only confirmed what I knew to be true: the world was unsafe, and danger lurked in the most innocuous places. It was a lesson I had learned with Lila's death, and over the years I saw it repeated over and over, an unrelenting pattern.

I looked over Thorpe's shoulder, trying to read the labels on the files, but they appeared to contain only dates instead of names. Finally he pulled out a folder and flipped through it until he came to a 46 green notebook with the word Memorandum embossed in gold across the cover.

"Great notebook, isn't it?" Thorpe said. "FBI issue. A friend of mine in the Bureau, Lucy Ranahan, gave it to me ages ago. I think it's positively Hooveresque. Unfortunately, they don't make them anymore." He licked his index finger and flipped through it. "Oh," he said, "it's James."

"Pardon?"

"James Wheeler, not John Wheeler. I remembered it wrong. Here's his old contact info. He was in his fifties then, not in the best of health. It's quite possible he's dead now. A much younger wife, though, if I remember correctly." Thorpe ripped the page out of the notebook and handed it to me. It had a name, address, and phone number.

"What's this?" I said, pointing to a sketch of a face beneath the number.

"Oh, just a habit. When I interview people, I draw them. I draw the victims, too, from photographs. Helps me get into the characters. I tried to get my editor to include the drawings in the book, but she said it sent the wrong message."

I wondered if he had drawings of Lila, of me. I reached for the book, but he held it out of my reach. "I promised you one name."

"Are there others?"

He didn't answer. We walked back through the house. In the entryway I paused in front of the fountain, stalling. I still wanted to ask him about the view. Close up, I could see that the water in the fountain was green and sc.u.mmy. Dead bugs floated on the surface.

"You want it?"

"Pardon?"

"The fountain. It was Flo's idea. I've been meaning to get rid of it. You can have it if you like."

"Thanks," I said, "I'll think about it," but we both knew I wouldn't. Then we were standing in the open doorway, and I knew the opportunity to ask him about the window had pa.s.sed. His garden looked shabbier in the morning than it had when I arrived. The lavender was dull and brown, and the small patch of earth needed weeding.

"See you next Sat.u.r.day?" he said.

I nodded. He stood at the door, watching me, while I fished through my purse for the keys and got in the car. Just as I was about to pull away, he ran out to the curb and knocked on my window.

"Comfortable shoes," he said.

"Comfortable shoes?" I thought for a moment he was providing me with a clue, offering some enigmatic puzzle that might lead me to Lila's true killer.

"On Sat.u.r.day," he said. "It's a walk to Mangosteen."

"Of course."

Driving the winding road down from Diamond Heights, I remembered a story I'd once told Thorpe, over a picnic at Lone Mountain. The story was about Boris, the German shepherd that had been in our family since Lila and I were children. In 1986, he had become very ill. It was terrible to see him that way, and we did everything we could to make him comfortable. All his life, he had decided each night when he went to bed which of us he would grace with his presence-our parents, or me, or Lila. He would enter the chosen bedroom with a great show, plopping down on his haunches and sniffing the air, before sauntering over to the bed and climbing on. As much as we loved him, over the years, each one of us had come up with countless schemes to lure Boris into one of the other bedrooms; he was a terrible snorer and he took up so much room in the bed, it was hard to get any sleep with him curled up at your feet. But after he became ill, we stopped playing those games. We realized that, one day before too long, we were going to miss that loud, wet snoring and his unwieldy bulk at the foot of the bed.

A couple of weeks before Boris died, when it was clear that he might pa.s.s away at any time, we made a schedule so that someone would always be at home. None of us could bear the thought of Boris dying alone. If one of my parents couldn't arrange to work from home, either Lila or I was allowed to stay home from school. One Tuesday it was my turn. Our habit on those days was to stay next to Boris's side in the living room, from which he rarely budged. I'd done just that all day long, stroking his fur and reading aloud to him, when the doorbell rang.

It was Roxanne, a neighbor girl from two houses down. I'd babysat for her family for a few years, but since she'd turned ten a few months before her parents had started leaving Roxanne and her little brother, Robbie, home alone. The moment I opened the door, I knew something was terribly wrong. She had a look of sheer panic in her eyes, and all she said was, "Robbie's choking! n.o.body's home!" I took a quick look back at Boris, who was staring up at me from his pallet on the living room floor. "I'll be right back," I promised. Boris let out a faint sound, lifted his head, and attempted to move. I could tell he was about to try to follow me, even though he'd not moved more than a few inches at a time in days. "Stay," I said, then bolted out the door and ran to Roxanne's house, where I found six-year-old Robbie, whom I'd never liked very much, writhing and blue-faced on the kitchen floor. I lifted him to his knees and did the Heimlich maneuver, and a big chunk of something flew out of his mouth. Roxanne, who was shaking and crying at this point, declared, "It was a frozen banana. I told him not to eat it!" I made sure Robbie was all right, told Roxanne to call her mother, and then raced home.

When I got there, Boris was lying on the floor of the entryway, perfectly still, eyes open but vacant. He wasn't breathing. He had no pulse. While I was performing the Heimlich on the bratty kid down the street, Boris had died trying to get to me. Even though my parents commended me for coming to Robbie's rescue, I never forgave myself for not being there for Boris, for letting him die alone.

Years ago, when I told the story to Thorpe during the picnic, he had listened intently. When I was finished, he remained silent for several seconds. I expected him to say something about what a sad story it was. I was shocked, then, when he finally spoke. "Wow," he said. "What a perfect ending."

There is an office on the third floor of Sloan Hall at Stanford, Thorpe had written in the final chapter of Murder by the Bay. In the office sits a man-tall, imposing, the kind of man whose very presence changes the chemistry in a room. His concentration is as fierce as his ambition. At this moment, perhaps, he is working on the Goldbach Conjecture, certain that he will one day find the proof. When he does, there will be no one to share the glory.

Looking back, I realized I should have put two and two together long ago. Thorpe hadn't discovered the ending in the process of writing the book. He had written the book toward his perfect ending.

Twenty-two.

WHEN I GOT HOME AT HALF PAST SIX, I threw my clothes into the washing machine, then showered to get the smell of Thorpe's house off my skin. Even though he hadn't smoked for two months, I came home reeking of stale cigarettes.

It was still too early to call the phone number he had given me. Despite my exhaustion, I knew I wouldn't be able to sleep, so I took Lila's notebook from its hiding place beneath my bed and drove to Hayes Valley. I parked on Octavia and walked down the narrow alley, past the graffiti-spattered mechanic shops, past the black leather corsets on display in the windows of Dark Garden. A line stretched into the alley outside the Bluebottle coffee kiosk. On more than one occasion I'd seen unsuspecting customers step up to the counter and order a "half-caf double latte" or "short soy hazelnut cap," only to be subtly rebuked by the barista, whose att.i.tude made it clear that if they wanted some hyped-up, tricked-out excuse for a good, solid cup of coffee, they could take their business to Starbucks. I'd never been much for the bells and whistles myself, and couldn't imagine watering my Coffea arabica down with soy milk or injecting it with flavored syrups. Bluebottle had no seating, just a small counter perched over the sidewalk, but in a way this added to the place's charm.

I breathed deeply, enjoying the huge aroma of the Yemen Sana'ani, before taking my first sip. I tasted hints of apricot, tobacco, wine, and spice. The first sip of the morning was always the best, when I could feel the cobwebs of my mind clearing, the blood rushing to my head. I tuned the world out and opened Lila's notebook, determined, once again, to try to make sense of it.

On the page where I'd left off, Lila had written down the Continuum Hypothesis: There is no infinite set with a cardinal number between that of the small infinite set of integers and the large infinite set of real numbers.

The next couple of pages contained notes on the problem's history. I was reminded of a conversation we had late one night in her bedroom, after our parents had gone to bed. I couldn't quite place when the conversation had occurred-maybe weeks before she died, maybe months?-but I remembered the gist of it.

The Continuum Hypothesis was special in that it was the first problem on David Hilbert's famous list of twenty-three unsolved problems, which he proposed in 1900. In the early sixties, someone had proved that the Continuum Hypothesis could never be determined to be either true or false. But the famous mathematician Paul Erdos had another take on it. His thought was that, if there were such a thing as an infinite intelligence, it might have the knowledge, which is lacking in humans, to decide whether the hypothesis was true or false.

"So unless the human race somehow manages to get infinitely smarter," Lila said, "the planet will die out without us solving this basic problem about infinity."

"What if your Goldbach Conjecture is the same sort of problem?" I asked. "What if you spend the next thirty years pursuing a proof that doesn't exist?"

"Then at least I'll know I tried," Lila said. "At least I'll know I did everything I could, and I didn't give up."

Every day since my meeting with McConnell, I had come up against the limits of my own knowledge, the frailty of my imagination. If the situation had been reversed-if it were my body that was found in the woods-I knew that Lila would not have taken some story in a book at face value. With determination, she would have examined the facts and methodically pieced the puzzle together. I was convinced that she wouldn't have stopped until she knew the truth. And I was certain it wouldn't have taken her twenty years to begin the search.

At eight a.m., I took the slip of paper from my wallet and dialed the phone number. A woman answered on the second ring. "Good morning," I said. "Is this the number for Mr. James Wheeler?"

"This is Delia Wheeler. Are you calling about a bill?"

"No."

A dog barked in the background. "Are you sure? Because the only person who ever called him James was his mother, G.o.d rest her."

"I promise I'm not a bill collector."

"This is Jimmy's number, then. Who am I speaking to?"

"You don't know me, but our paths crossed a long time ago. Lila Enderlin was my sister."

"Who?"

"Lila Enderlin."

She paused. I could hear the dog, closer now, panting near the phone.

"We don't know anything about that," Delia said.

"I'd just like to come by and talk to Mr. Wheeler for a few minutes, please."

"The police talked to him thirty years ago," she said. "He told them everything."

"Twenty," I said.

"What?"

"It was twenty years ago that Lila died."

Another pause. "I could've sworn it was 1979. Lord, if my mind goes, too, we're sure up the creek."

"Are you still living on Moultrie?" I asked.

"We are."

"I can come by anytime."

I fully expected her to shoot me down, at which point I'd have to start pleading, so I was surprised when she said, "Well, I guess we'll be here all day. Jimmy can't go out anymore and I don't like to leave him alone."

"I'll be there in an hour. Thank you so much for seeing me."

The house on Moultrie was a brown-shingled cottage with dark yellow trim, the front door situated just a few feet from the sidewalk. The street was packed with cars, so I had to drive around for a couple of minutes before finding a spot.

I was just about to ring the bell when the door opened. A tiny, pale woman, about four foot eleven and no more than ninety-five pounds, stood before me in a Google T-shirt and black pants. Her long brown hair was in a ponytail, and she wore pink blush and matching pink lipstick. She was even younger than I expected-probably in her early sixties.

"Ellie Enderlin," she said, studying my face. "My goodness." She seemed about to say something else, but instead she just stepped aside to let me in.

"Thank you for letting me come over on such short notice."

"Well, I doubt I can help you, but it's nice to have a visitor."

To the right of the entryway was a blue curtain, partially opened to reveal a nook just big enough for a bed. On a narrow table at the foot of the bed was a small television, the lights of which played over a yellow quilt. No sound came from the TV. There was someone in the bed-James Wheeler, I a.s.sumed-but because of the curtain I could only see his feet, white and bony. Next to the feet, a small black dog slept. We pa.s.sed through the entryway into a small, immaculate living room. It was a shotgun house, with the kitchen in the back, and a bathroom off the kitchen. A tea kettle rattled on the stove.

"Sorry for the mess," she said. "I didn't have time to clean."

"It looks perfect." I sniffed the air-ginger and cinnamon. "What smells so good?"

"Oh, that's just coffee cake. I'd have made you lunch if you came later."

"You didn't have to do that."

"I grew up in Mississippi," she said, opening the oven to examine the cake. "My mother would roll over in her grave if I had a guest over and didn't offer them something to eat. Just last week Matthew-that's our oldest-took me to a lady's house out in Pinole to buy a wheelchair that he found on the computer. For Jimmy, you know. The lady didn't so much as offer us a gla.s.s of water."

Only after we were sitting at the table with the cake arranged on a pretty china platter between us did Delia Wheeler bring up the purpose of my visit.

"It's that Peter McConnell fellow that did it," she said, looking into my eyes with conviction. "I read that book, it's clear as day he was the one. It was a terrible thing. I feel so for your parents, hon. For you, too, but especially your parents. I can't imagine if somebody did something like that to one of my boys. It still breaks my heart to think of it."

I nodded. "It's been a long time, but not a day goes by that I don't think about my sister."

"If I remember correctly, that McConnell fellow just up and disappeared. Did they ever end up arresting him?"

"No."

"That's a shame. Nothing can bring her back, I know, but if it was my own, I'd want somebody to be held accountable."

She sipped her tea and chewed thoughtfully. "Honestly, hon, I'm not sure why you're here. I don't see what we can do for you."

"I understand your husband talked to my sister the night before she died. I thought he might be able to fill in some blanks for me."