Charlie Chan in San Francisco

A month after the events on the Honolulu Paradise, Jason Fairfax III finds himself embroiled in a new mystery. Secret Army plans have gone missing from his father's Menlo Park plant, and the army has decided his father is the most likely suspect for the theft. Though estranged from his parents, Jason is convinced that his father is innocent. The army and the San Francisco police coerce him into introducing Inspector Charlie Chan to his parents' home under the guise of a prospective father-in-law, an awkward subterfuge because Jason is still screwing up his courage to propose marriage to Rose Chan, Charlie's "number-one daughter." The army hopes that Charlie Chan will find the plans in the Fairfax Atherton home, and they rather expect to put Jason Fairfax, Jr., Jason's father, behind bars once the Honolulu inspector does so. Jason intends to clear his father's name, but doing so may not be as easy as he expects. Before the stay is over, a suspected Japanese spy, a Hawaiian crime lord, a traitor, betrayal, a reporter who knows more than she should know, and (of course) murder make it clear that there is more to this theft than meets the eye. And, inevitably, three of Inspector Chan's children arrive to provide their own dubious form of help. What could go wrong?