A pair of musicians are performing their act when one of them is almost electrocuted. Mannix is hired to look into the matter. But the detective faces twists almost immediately. For starters, the woman who hired Mannix isn't who she said she was. Mannix also needs to act fast before another attempt on the musician's life is made.
Joe Mannix receives an urgent phone call from his friend George Lassiter asking him to come to Albuquerque because of a problem with Lassiter's daughter Jeannie, who is also Joe's goddaughter. Mannix arrives quickly only to be told that the problem has been solved. Sensing that he's not receiving the whole story, though, Mannix decides to conduct his own investigation -- leading him to discover that his friend is involved in a novel form both of kidnapping and of paying the ransom.
Jenny Cole, the daughter of a friend of Joe Mannix, awakens after almost a year in a coma following a hit-and-run accident. But the celebration of her return to health is soon cut short when someone tries to kill Jenny. This leads Mannix to conclude that Jenny must have seen something on the day of the accident that she shouldn't have seen -- and that someone wants to tie up that loose end by "putting her to sleep" permanently.
At the start of a long weekend, off to a fishing vacation with friend Tony Elliott, Mannix stops at Tonys office so Tony can pick up a set of fishing flies. They walk in on a methodical heist of the businesses in the building. Mannix is trapped in the building, playing a cat and mouse game with the three burglars.
Mannix travels to an island that's part of a South American country. Mannix's client wants to repay the man for the saving the life of the son of the client some years earlier. But Mannix soon discovers the case is more complicated than he bargained for. The man he's searching for is part of a plot to assassinate the president of the country. Just as Mannix is putting the pieces together, he's captured by the conspirators.
The conspirators assassinate the president of a South American country and successfully frame Mannix for the killing. Now, the detective must dodge the authorities and hunt the conspirators as he tries to clear his name.