The Brubaker house always smells like other people's dinners. Mara has babysat three-year-old Theo eleven times now. Same rules every time: monitor on, door cracked, bed by eight. It's 9:40 and the living room is dark except for the little green screen. Theo is a small white smudge, asleep on his side. Then the screen hisses with static, and when it clears, the smudge is sitting straight up, facing the camera.

Mara isn't going up there. Not yet. She texts Theo's mom: 'Quick question, does Theo ever sit up in his sleep?' The dots appear, stop, then appear again. The reply lands: 'We don't have a baby monitor in his room. We never bought one.' Mara looks down at the green screen in her hands. It is clearly showing a crib.

Mara drops the monitor on the couch and bolts up the stairs two at a time. Theo's door is shut, just like always. She shoves it open. The crib is empty. The whole room is empty. But on the wall above the crib, drawn in green crayon, is a little screen with a girl inside it, and the girl has her exact face.

Mara backs away from the wall, but the crayon screen begins to glow. The girl drawn inside it turns her head and looks right at Mara. 'Eleven nights,' the drawing mouths. 'One more and I'm out.' Mara runs for the stairs, grabs the real Theo from the couch downstairs, and carries him out the front door into the night.