Lieutenant Tanaka is murdered while working undercover. The official police report states that Tanaka died in a car accident, but Magnum believes that something is being covered up and sets about trying to answer the many questions about his friend Tanaka's death, uncovering switched identities and drug-running in the process.

Magnum is trying to protect Carol, who is in the middle of a particularly controversial court case, when he is hired by a woman from the mainland to help locate the birth certificate for the child she gave up for adoption 30 years ago. In doing so he becomes embroiled in Carol's personal life, as he discovers a powerful secret about her parents and her true birthright that could shatter her.