"But the bullies never picked on Diogenes."

"Children have a sixth sense about that kind of thing. And to think Diogenes was younger and smaller than Aloysius."

"How did the two brothers get along?" D'Agosta asked.

"Ambergris, you're not getting forgetful in your old age, are you, dear? You know Diogenes hated his older brother. Diogenes never cared for anyone but his mother, of course, but he seemed to put Aloysius in a special category altogether. After the illness particularly."

She paused, and for a moment her mad eyes seemed to dim, as if she was peering far into the past. "Surely, you remember Aloysius's pet mouse."

"Oh, sure. Of course."

"Incitatus he called it, after the emperor Caligula's favorite horse.

He was reading Suetonius at the time, and he used to walk around with the tiny beast on his shoulder, chanting: 'All hail Caesar's beautiful mouse, Incitatus!' I have a perfect horror of mice, you know, but the little white thing was so friendly and calm I found myself able to bear it. Aloysius was so patient with the creature, he loved it so. Oh, the tricks he taught it! Incitatus could walk upright on his hind legs. He must have responded to a dozen different commands. He could fetch a Ping-Pong ball for you and balance it on his nose like a seal. I remember you laughing so, dear, I feared your sides would split."

"I remember."

Great-Aunt Cornelia paused. Even the impassive guards seemed to be listening.

"And then one morning young Aloysius woke to find a wooden cross planted at the foot of his bed. A little cross, no more than six inches high, beautifully and lovingly made. Incitatus had been crucified upon it."

D'Agosta heard Laura Hayward inhale sharply.

"Nobody had to ask. Everyone knew who'd done it. It changed Aloysius. He never had another pet after Incitatus. As for Diogenes, that was just the beginning of his, ah, experiments on animals. Cats, dogs, even poultry and livestock began to disappear. I recall one particularly unpleasant incident with a neighbor's goat…"

At this, Great-Aunt Cornelia stopped speaking and began to laugh, quite softly, under her breath. It went on for a long time. Dr. Ostrom, growing alarmed, frowned at D'Agosta and pointed to his watch.

"When did you last see Diogenes?" D'Agosta asked quickly.

"Two days after the fire," the old woman replied.

"The fire," D'Agosta repeated, trying not to make it sound like a question.

"Of course, the fire," Great-Aunt Cornelia said, her voice suddenly agitated. "When else? The dreadful, dreadful fire that destroyed the family and convinced my husband to bring me and the children up to this drafty mansion. Away from New Orleans, away from all that."

"I think we're done here," Dr. Ostrom said. He nodded to the guards.

"Tell me about the fire," D'Agosta pressed.

The old woman's face, which had gone almost fierce, now took on a look of great sorrow. Her lower lip trembled, and her hands twitched beneath the restraints. Despite himself, D'Agosta couldn't help but marvel at the suddenness with which these changes overtook her.

"Now, listen," Dr. Ostrom began.

D'Agosta held up his hand. "One minute more. Please." When he looked back at Great-Aunt Cornelia, he found she was staring directly at him.

"That superstitious, hateful, ignorant mob. They burned our ancestral home, may the curse of Lucifer be on them and their children for all eternity. By that time, Aloysius was twenty and away at Oxford. But Diogenes was home that night. He saw his own mother and father burned alive. The look on his face when the authorities pulled him from the basement, where he'd gone to hide…" She shuddered. "Two days later, Aloysius returned. We were staying with relatives by then, in Baton Rouge. I recall Diogenes taking his older brother into another room and closing the door. They were only inside for five minutes. When Aloysius came out, his face was dead white. And Diogenes immediately walked out the front door and disappeared. He didn't take anything, not even a change of clothing. I never saw him again. The few times we heard from him, it was either by letter or through family bankers or solicitors, and then nothing. Until, of course, the news of his death."

There was a moment of tense silence. The sorrow had left the old woman's face, leaving it calm, composed.

"I do believe it's time for that mint julep, Ambergris." She turned sharply. "John! Three mint juleps, well chilled, if you please. Use the icehouse ice, it's so much sweeter."

Ostrom spoke sharply. "I'm sorry, your guests have to go."

"A pity."

An orderly arrived with a plastic cup of water. He handed it gingerly to the old woman, who took it in her withered hand. "That's enough, John. You are dismissed."

She turned to D'Agosta. "Dear Ambergris, you're leaving an old woman to drink alone, shame on you."

"It was nice seeing you," D'Agosta said.

"I do hope you and your lovely bride will come again. It's always a pleasure to see you… brother." Then she abruptly bared her teeth in what seemed half-smile, half-snarl; raised a spotted hand; and drew the black veil down over her face once again.

Somewhere, a clock chimed midnight, its deep, bell-like tones muted by the plush drapes and hanging tapestries of the library in the old mansion at 891 Riverside Drive.

D'Agosta sat back from the table and stretched in the leather armchair, fingertips working the kinks out of the small of his back. This time the library felt a lot more cheery: a fire was crackling atop wrought-iron firedogs, and light from half a dozen lamps threw a mellow glow into the remotest corners. Constance was sitting beside the fire, sipping tisane from a china cup and reading Spenser's Faerie Queene. Proctor, who had not forgotten D'Agosta's own taste in beverages, had drifted in a few times, replacing warm, half-finished glasses of Budweiser with chilled ones.

Constance had produced all the materials Pendergast saved concerning his brother, and D'Agosta had spent the evening poring over them. Here, in this familiar room, with its walls of books and its scent of leather and woodsmoke, D'Agosta could almost imagine Pendergast at his side, helping him take up the long-cold trail, pale eyes glittering with curiosity at the onset of the chase.

Except there was precious little here to chase. D'Agosta glanced over the documents, clippings, letters, photographs, and old reports that littered the table. Pendergast had clearly taken his brother's threat seriously: the collection was beautifully organized and annotated. It was almost as if Pendergast knew that, when the time ultimately came, he might not be around to face the challenge; that the task might be left to others. He'd saved every scrap of information, it seemed, that he had been able to obtain.

Over the last several hours, D'Agosta had read everything on the table two and, in some cases, three times. After Diogenes had severed his connection with the Pendergast clan following the death of his mother and father, he had gone largely into hiding. For almost a year, there was no word at all. Then a letter arrived from a family lawyer, asking that a sum of $100,000 be wired to a Zurich bank for Diogenes's benefit. This was followed a year later by another, similar letter, demanding that $250,000 be wired to a bank in Heidelberg. The family rejected this second request, and it prompted a response from Diogenes. That letter now sat on the table, sealed between two panels of clear Lucite. D'Agosta glanced once again at the spidery, meticulous script, so curiously inappropriate for a boy of seventeen. There was no date or location, and it was addressed to Pendergast: