Ellen Barton hires Mannix to determine that her husband's death in a scuba-diving accident was no accident.

The private secretary of a murdered PI comes to Mannix for help. She doesn't remember much about her boss' cases, but men are trying to kill her anyway.

A man hires Mannix to track down a pedestrian he may have ran over with his car. But the only witness claims nothing happened, and men threaten Mannix figuring that he killed the pedestrian.