On robbery detail, Joe Friday investigates the possibility that a valuable ring that has been taken to a pawn shop is stolen. It certainly seems to be, and the man who took it there is quickly apprehended. His interrogation turns up nothing, and he is let go.
When an anonymous note comes in, Joe and partner, Frank Smith follow up to find a box full of jewelry. Comparing it to recent reports of robbery, the owner is quickly matched to it.
Friday and Smith go after their man. Though he has moved, with no forwarding address, he still is easy to find. With the right pressure put on, he sends Friday on the trail to the real robber.