The Bob-Whites attract attention when they are given a Model T Ford to auction for a hospital rummage sale. When the car breaks down, they are helped by a stranger who is run down by a van before their eyes! Trixie becomes determined to find out who is responsible. But the victim can't even remember his own name! When he disappears and the Model T is vandalized, Trixie is the only one who believes he is innocent. The girl detective vows to find the vanishing victim and solve the mystery.