Milo woke to a soft click. The last light had switched off. He'd dozed off in the beanbag, and his comic had slid to the floor. The library was closed, dark, and locked tight. It smelled of dust and old glue. Then he heard it: every shelf was breathing. Books slid their spines a half-inch out, then back, in and out. A voice whispered, "Stay quiet. Don't wake them all the way."

Milo froze and stayed dead quiet. He looked around the dark for who had whispered. A small girl crouched behind the front desk, waving him over. "Hurry," she breathed, "before a loud one notices you." He crept toward her on his hands and knees.

Behind the desk, the girl pressed a finger to her lips. "I'm Posy. I fell asleep here too, ages ago." She pointed at a thick red book on the top shelf. "That one's the Keeper. If it opens its cover, everybody wakes. We have to slip out before it does."