The night shift is quiet except for the machines breathing down the hall. The gray cat, Marrow, walks ahead of me like he owns the place. By March I figured out the rule nobody says out loud: wherever Marrow curls up to sleep, that bed is empty by dawn. Tonight he stops outside Room 14. Then he turns and looks straight at me with flat yellow eyes.

I'm done being scared of a cat. I scoop Marrow up before he can settle and carry him to the far end of the hall. If he can't sleep by Room 14, maybe the rule breaks. He goes stiff in my arms and lets out a low growl I've never heard from him.

Marrow twists out of my arms and hits the floor running. He goes straight back to Room 14 and lies down across the doorway, like nothing happened. But now there are two of him. A second gray cat sits at the other end of the hall, watching me.

I look from one cat to the other. The second one stands, stretches, and walks toward the room next to mine, where old Mrs. Okafor sleeps. I understand now. Marrow marks them, but there's a whole pack, and they're spreading down the hall. I run for the phone to wake the other nurses before every door is claimed.