Lionel Twain invites the world's five greatest detectives to a 'dinner and murder'. Included are a blind butler, a deaf-mute maid, screams, spinning rooms, secret passages, false identities and more plot turns and twists than are decently allowed.
Mary Whitman has gone to Reno to obtain a divorce. While there she is arrested on suspicion of murdering a fellow guest at her hotel (which specializes in divorcers). There are many others at the hotel who wanted the victim out of the way. Charlie comes from his home in Honolulu to solve the murder.
Charlie's investigation of a phony psychic during the 1939 World Exposition on San Francisco's Treasure Island leads him to expose a suicide as murder.
A dangerous amnesiac escapes from an asylum, hides in the opera house, and is suspected of getting revenge on those who tried to murder him 13 years ago.
While visiting the circus with his family, Charlie is recruited by the big top's co-owner to investigate threatening letters that he's received.
Charlie impersonates an employee of the U.S. government to foil an espionage plot which would destroy part of the Panama Canal, trapping a Navy fleet on its way to the Pacific after maneuvers in the Atlantic.
Sir George hires Hillary Gatt to find out more about Eric who wants to marry Lois. Gatt is murdered and the couple, married, run off to India. Old friend John Beetham sympathizes with the bride who sees that her hubby is a liar and drunk. John and Lois fly to San Francisco. Eric shows up and tries to kill John, but Scotland Yard's Lt. Charlie Chan intervenes. Chan fans may be disappointed in this globe-trotting mystery, however, as the detective (played by Korean actor E.L. Park) only appears in a few scenes.The film is more noteworthy for its introduction of Boris Karloff to sound features, in a small role as a servant from Sudan who mutters inscrutable nonsense about the whims of the desert.
A pair of murders in Rio de Janeiro leads the local police to call the famed detective. Charlie is puzzled, at first, when it appears that one of the murderers is killed by the first victim's widow.