Factual error: In the scene when the two criminals are in the hardware store, two vehicles are parked outside that are clearly late 1960's automobiles, despite the film being set in 1959. (00:15:25)
Continuity mistake: When Robert Blake and his accomplice take the father and son to the basement, Blake pulls the string on a hanging lamp and the room becomes fairly bright. A moment later, Blake's accomplice pushes the father into the same room, which is now significantly less well lit, even though the same hanging light is still on.