A black box sat strapped to the cross brace, flat as a deck of cards.

Two white zip ties ran through slots in the plastic, and a green light blinked along the narrow edge.

“Who put that there?”

“Daddy did.” She said it into her collar.

I reached under and touched it.

It was warm, the way a phone is warm after a long call, and one corner had split so the metal edge showed through the plastic.

Sophia pulled my wrist back with both hands.