When the elderly woman sponsoring a treasure hunt is murdered on board her docked ship, Charlie Chan must deal with a treasure map in four pieces, the ghost of a hanged pirate, a talking parrot, a recalcitrant sea captain and several suspicious passengers - and a second murder.

Charlie Chan, with son Jimmy on a week's pass from the Army, takes up a request for help at a castle-home, miles from anywhere in the American desert south-west and inhabited by an eccentric, reclusive historian and his wife, a descendant of Lucrezia Borgia. Once there, he finds the request's legitimacy denied by all who are present, but still necessary as one houseguest has already been murdered, the other guests are at each other's throat, and the Borgia-related chatelain is suspected...