Joe Friday gos out to investigate a robbery at a grocery store. A story of a masked bandit is told, and the details of how he robbed the place. In voiceover, Joe compares notes to other cases of robbery, and patterns begin to emerge. A plan is deviced to spring a trap, but has the crook moved on?
Crimes with the same method appear in a neighboring city, and Joe has to work with those cops and businesses to work his plan.
It doesn’t take long for a robber to be picked up who fits the profile that Friday put together. Eavesdrop on the interrogation and lineup process as Joe Friday grills his suspect. witnesses to the lineup disagree. Is the suspect the right man? More reports of robbery seem to prove the point, and what they have is a copycat robber.
Though Joe has caught this burglar, his masked robber is still out there.