The next day found Lyra and Pan doing something they really weren't supposed to be doing.

But, Pantalaimon thought with a sigh, how was that different from any other day?

He was crouched as a mouse on Lyra's shoulder, and they were trying to break into the Library.

"Drat it, Pan," Lyra said, wiping sweat off her forehead. It was only midmorning, but already the sun was fierce. "I don't think I can get this new lock undone." She struggled with a length of wire she was trying to use to open the new lock on the small window leading into the Library's most secluded corner. "I don't understand why them Scholars had to lock this one up-nobody uses it, anyway."

"Except you," Pan reminded her. "Maybe they noticed how you left it open from yesterday. We ought to try the window on the west side-we can get there from the chapel rooftop."

Lyra considered it. The chapel roof was risky-parts of it were steeply sloped, and the tiles always threatened to come loose. Still, though, it looked like their only chance. "All right, Pan."

She took off running across several flat rooftops, leaping short distances between them with a speed that made Pan turn into a sparrow and fly next to her. They reached the chapel in only a few minutes, and Lyra was hardly even out of breath.

Now comes the hard part, thought Lyra. Crouching on the edge of the rooftop closest to the chapel, she took a deep breath. The edge of the chapel roof was a good five feet away-a longer jump than usual. If she missed, it would be a long fall down to the hard stones of the alleyway below. Pan had already fluttered across, and sat on the head of one of the statues adorning the roof, waiting for her.

She jumped. The thrill of being in midair almost made her lose her purchase when she hit the rooftop. Her foot slipped when she landed and a couple of tiles skidded lose, but she grabbed a statue's head to steady herself.

Looking up, she grinned in triumph at Pan, who turned into a cat just so he could look disdainful.

She laughed. "C'mon, Pan. Stop looking smirky and let's get to the Library."

Thankfully, the west window proved to be unopened. Lyra levered it up, trying to make as little noise as possible. It squeaked anyway, and she caught her breath in fear, looking around inside to see if any Scholars came rushing at the noise. Nobody came, and Lyra stepped inside, closing the window behind her this time. Lyra picked Pan up, and he turned into a ferret to drape around her neck, leaving her hands free.

The cool air and musty smell of the Library was quite a change from the blistering heat of the rooftops. Lyra blinked and looked around, trying to accustom herself to the dim light.

They were on the third floor of the Library. The room was cylindrical, and it went up for several more floors. The floor Lyra was standing on extended around the room, but in the center there was empty space, so that she could look down and see the lower floors. She did so, and she didn't see any Scholars absorbed in books or otherwise occupied.

There didn't seem to be any Scholars on this level, either. Lyra went past the bank of windows from which she had entered and came to the beginning of the shelves of books that wrapped all around the walls.

"What are looking for, exactly?" Pan whispered.

"Anything about merfolk," she whispered back. It never hurt to be careful-some scholars had ears like bats, even when absorbed in study. She examined the books.

Some looked very old, and the languages on the bindings were ones she didn't know. Others looked newer, but all looked much older than she was. The subjects seemed to a dull lot-theology, anatomy, natural sciences, biology, mythical creatures-

Mythical! Hadn't that been what Uncle had said? Lyra pulled the book from the shelf, ignoring the minor dust storm that resulted. The tome was large, and heavy. She toted it over to the nearest table, and it thumped when she set it down. Looking quickly behind her, she was satisfied that no-one had heard the noise and sat down to study her newfound treasure.

It was covered in leather, and the title was in curly silver writing. "Nimere's Book of Creatures Magical and of the Myths of Man," Pan read out. "Sounds scholarly enough."

"Yeah," Lyra said, more curious now. "I bet it's got all sorts of things about mer-people in it." She pulled open the inside cover. There was no title page, or table of contents. It just started at the first mythical creature, and catalogued them all. The pages rustled as Lyra leafed through them. It didn't appear to be in any particular order. She went past pictures and descriptions of faeries, gnomes, night-ghasts…mer-people!

She turned the page to find an illustration of a strangely beautiful creature-a woman with a fish's tail. She had long, dark hair that streamed over the page, and her eyes were weirdly slit-pupiled, like a cat's. Her skin was white, and some deft artist had used crushed mica to give her scales a glittering appearance.

What made Lyra start, though, was that the mer-woman had fins growing out of her wrists and upper arms, and that her fingers were webbed.