Magnum is called back to service by Admiral Hawkes, who has reason to suspect that there is a security leak at his base that is leaking coded information, and Magnum's prime suspect is the fiancee of the Admiral's son.

An old comrade of Higgins' brings hisInky Gilbert Traveling Carnival & Midway to Hawaii. But when one of the performers is fatally stabbed, Higgins asks Magnum to investigate. Working undercover as a carny, aided by Rick, Magnum learns that even before the killing, the carnival had been experiencing a string of "accidents", and must pinpoint exactly who is trying to force the show out of business.