Mike took the papers back and compared the two writing styles. I knew what he was thinking. We’d have to bring in another expert-someone familiar with the very unscientific field of handwriting analysis. One clue that seemed promising at two o’clock in the morning now created a new level of obfuscation.

“The second page-that quote on the back of the slip-that’s Tina’s writing,” Jill said. “But she didn’t fill out this form. We have several early editions of the Lewis Carroll work, all of them quite rare. Maybe another person asked her to make the request to see one of these books.”

Maybe someone who didn’t want to be associated with the request filled out the call slip, counting on the fact that he-or she-could persuade Tina to deliver it and retrieve the book. Maybe it was the person who killed her.

“Where are the books?” Mike asked. “I don’t see a frigging book in here.”

Mike, Mercer, and I were standing in the middle of Astor Hall, one of the most magnificent interior spaces in New York. Jill had gone off to find the chief security officer to ask him to guide us through the enormous building.

“It’s not a lending library, Mike. It’s a home for scholars to use, for research,” I said. “Books have to be accessed through a formal system. They’re not out on open shelves, and they never leave.”

“Unless they’re stolen. So where the hell are they?”

“Upstairs, in carefully maintained private collections,” I said. “And under your feet, in the stacks. You’ll see.”

Mercer was walking around the great vaulted space. “Looks like we’ve time-traveled back to inside a medieval castle.”

The great hall, dressed entirely in white marble, had a self-supporting vaulted ceiling that covered the space between the two broad staircases leading up to the second floor. Four giant torchères-also marble-stood sentry around the large, empty room.

“Did you see her hand shake?” I said, whispering so that my voice didn’t echo throughout the hall.

“Jill’s?” Mercer asked. “I missed that.”

“When Battaglia and I were talking to her yesterday and McKinney jumped in, he referred to Tina Barr as a thief and a forger.”

“And you said Jill didn’t seem to buy in to that.”

“Yes. But someone working in here must think so.”

“What’s your point?” Mike asked, standing under one of the arches across the room.

I walked toward him so that I didn’t have to shout. “How can Jill say for sure that the writing on the call slip wasn’t done by Tina?”

“You mean, if Tina was capable of forgery, maybe she intentionally wanted it to look like someone else wrote it out?”

“That’s possible. Once she turned in the original slip, it would become the permanent record that the library would have for the request. That’s who they’d look to if the book went missing.”

Mercer came up behind me. “It’s also possible Jill got the shakes ’cause she recognized the penmanship on the slip, Alex. Maybe it’s given her an idea about who wrote it but she chose not to tell you just yet.”

We heard her approach on the marble staircase and stopped talking.

“Why don’t you come this way?” Jill said, pausing halfway down.

We crossed the room, our footsteps echoing throughout the hall, and followed Jill as she turned and walked up to the second floor. At the top, a man about my height with a thick build was standing cross-armed, dressed in a drab green uniform.

“This is Yuri,” Jill said, introducing him to each of us. “None of the security supervisors is here yet. He’s one of our engineers, so just tell us what you’d like to see and we can get started.”

“Top to bottom,” Mike said. “Entrances, exits, any way in or out of this place.”

“Obviously,” Jill said, “we’ve just come in the front door.”

“Is that how the public enters?”

“Most of the time, Detective. There’s also a smaller entrance on the Forty-second Street side. Yuri,” she said, “why don’t we start upstairs and work our way down?”

“What’s your security like?”

“Since September 11 it’s been a lot tighter. Our doors open at ten most weekdays. Guards check bags on the way in and on the way out.”

“I saw two metal detectors at the door,” Mike said. “They good enough to catch a thief with a razor blade or knife coming through?”

“So you know how the bad guys used to cut out the desirable pages?” Jill was a few steps ahead of us, with Yuri. “A thing of the past, Mike. Between metal detectors and the arrest of a few major map thieves, those particular tools have become obsolete.”

Yuri was leading us up another flight of stairs.

“You mean people don’t steal old prints or maps out of books anymore?”

“Sadly, the thefts go on. It’s just that the methods change. The bad guys have moved on to dental floss.”

“Floss?”

“Try it, Detective. Wet some floss. Soak it for a while to stiffen it up. Keep it moist by balling it up inside your cheek when you get to the library. The thieves have found it just as effective for ripping out pages with exactly the same result. Takes about ten minutes to soften up the old paper by applying the floss to it, so it’s a bit more nerve-racking than the old-fashioned technique. But it works just fine.”

“Not even against the penal law. Armed with a dangerous instrument-wet dental floss,” Mike said, trying to catch up with Jill. “You sure got a lot of steps.”

“All part of the master plan. The first floor has that grand open space, and a periodical room that the public was allowed to use from our earliest days. Then up to the second floor-you’ll see our offices later-where the private collections are housed, and then up to the third level, to the great reading room. The nineteenth-century design idea was to lift the scholars away from the noise and pollution of the street so they could get their work done in the lightest, airiest part of the library. Still a good idea. Is this where you did your college research, Alex?”

“The reading room? Yes, it is.”

“It’s been completely restored to its original condition. You’ll hardly recognize it,” Jill said, pausing at the top of the steps.

Yuri took a key from among the many on the ring that dangled from his belt. While he unlocked the massive wooden doors, I looked up to the barrel vault on the ceiling, at the brilliant painting of Prometheus bringing the gift of fire to man, which soared in the rotunda overhead.

He stood back to let us into the room. Mike and Mercer entered before me, and both seemed stunned by the beauty-and size-of the Rose Reading Room.

“Go ahead,” Jill said. “There’s a quarter of an acre of space in here, meant to accommodate seven hundred scholars. It’s one of the largest uninterrupted rooms in the city-almost the full length of two blocks. For me, it’s the heart of the place.”

Library table after library table with aisles on either side lined up in rows from end to end. Atop each were lamps and ports to service laptops at each station.

“It practically glows in here now,” I said.

The large multipaned windows that flanked the room flooded it with morning light. “Can you imagine?” Jill asked. “That glass was all painted black during World War Two, and stayed dark until only a few years ago, with this recent renovation.”

I walked along the parquet floors in search of the table at which I’d situated myself day after day to work on my senior thesis more than fifteen years ago. I looked up at the ceiling-perhaps the most beautiful in the city-for a marker among the hanging chandeliers, a gilded cherub whose once-tarnished wings now gleamed again. She was still surrounded, as I remembered her, by coffers ornamented with angels and satyrs, and luminous paintings of blue skies and puffy white clouds in the style of the old masters.

I sat in one of the chairs and leaned back to take in the murals and all the detail that seemed to have been refurbished to its original brilliance.