When a doctor who was a nurse during Magnum's days in Vietnam is accused of poisoning patients, he tries to clear her name, but is puzzled by her and her husband's rebuffing his offer of assistance and irritated by an agressive reporter.

Higgins sends Magnum to collect a valuable Kenzan porcelain plate, newly purchased by Robin Masters, from the airport, but the artifact, which was entrusted to the care of a samurai warrior named Tozan while in transport from Japan, has been stolen by a ninja. Magnum teams with the samurai, but they must work fast, as the samurai code of honor dictates Tozan must commit Seppuku if the precious plate isn't retrieved.