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 calls the parents instead of texting. 'Get out of the house,' the mom says fast, not surprised at all. 'We never bought a monitor because the last sitter left one on. She's still in it. Don't let Theo see the screen.' Behind Mara, the green light flickers, and a small voice from the speaker says, 'Too late.'

Mara grabs the warm, sleeping boy and runs for the front door. It opens easy. She makes it to the lawn, gulping cold air, Theo blinking awake in her arms. The green light in the window flickers once, twice, then dies. Whatever was in that monitor, it stayed inside. She does not go back for her phone.