Three children, Darryl, Kirk and Janet want to be rid of their priggish friend Trudy so they enter a big store and steal a battery knowing that not wanting to get involved she'll leave, which she does. The three had intended to replace the battery but forget when they realize that they've been locked in. Eventually they get out through a skylight but once back on the ground they bump into a thief who's acting as a lookout for a gang who are tunneling through the store's basement wall into the jewelers next door. The three are caught and locked up but are rescued by Trudy who'd been looking for them. They call the police who arrest the robbers and a police sergeant who thanks them for their action warns them that even stealing a small item such as a battery could lead to a life of crime.