A desk-type security agent involves the Minus Five team in a dangerous duel with jet-boats when two men are discovered tapping an undersea cable and selling information to a foreign power.

The Minus Five team play cops and robbers with a pearl smuggler, and one of the team becomes trapped in an underwater cave.

The Minus Five team become involved in a lover's quarrel, which quickly turns very serious when the girl involved is trapped in a cage on the sea bed, and all evidence points to attempted murder.