AllMovie

To test the honesty of his two nephews, old Adam Thompson (William H. Wright) tells them about a secret map leading to a valuable piece of land, then lets them know that the map is locked in his safe. He then sets up an infrared camera in front of the safe to find out if either nephew is capable of robbery. Unfortunately, the map vanishes even though the safe is never opened--and when Adam's foreman Frank Jarrett (Crahan Denton), who ends up in possession of the map, is murdered, Adam's nephew Harry (a young Bert Convy) is arrested for the crime. It looks like Perry Mason (Raymond Burr) is up against a good old-fashioned "locked room" mystery this time.