In October 1983, Jeff Nelson returns to Santa Barbara seeking his former fiancee Joanie Krans a year after an East Coast job transfer resulted in their breakup. His visit violates their painful separation pact but he urgently needs her expertise as an amateur naval historian in analyzing covert photographs of a strange vessel sunk nearby in the Pacific Ocean off Ellwood Canyon.
Joanie identifies the surprising wreckage and offers to help locate it, but someone determined to stop the search dispatches gunmen to kill them. Unscathed, they learn the mastermind's identity and begin a pursuit which is unexpectedly joined by a wealthy Oriental businessman from Seatlle wanting revenge for the man's murder of WWII compatriots. An aerial hunt takes the three of them to the Sierra Madre Mountains in central California where they confront the killer and his henchmen. He escapes but leaves behind a priceless cache of gems that Nazis had taken from Holocaust victims.
Back in Southern California, Jeff discovers something unique at the killer's abandoned ranch which could aid the new search. Joanie enlists the help of a friend, who joins the team and begins a relationship with the charming Oriental man, at least twenty years older.