While Charlie Chan and his number one son, Lee, are aboard a New York-bound transatlantic liner returning from Germany in their previous adventure (Charlie Chan at the Olympics), they have a run-in with a mysterious woman, named Billie Bronson, who secretes a package in the trunk of the Chans. After the liner docks, Chan and Lee are met at the pier by Inspector Nelson and two rival reporters, Joan Wendall and Speed Patton.
Billie, who left the country hurriedly a year ago when sought as a material witness in a political scandal, has returned to "blow the lid off the town". She follows the Chans to their hotel and attempts to regain her package from the trunk, only to be interrupted by Lee. She then goes to the "Hottentot Club", where "candid-camera night" is in full swing, followed by Lee. Already present are Joan and Speed. Billie is mysteriously murdered and Charlie is summoned from a police banquet in his honor. Present in the room with the body are club manager Johnny Burke; club dancer and Burke's girl-friend Marie Collins and the two reporters.
While Charlie seeks a motive for the murder, a second body is discovered in his hotel room, the package is missing from Charlie's trunk, and it is realized that it must have contained her diary. Charlie neatly puts together a few scattered clues and then springs a trap to confirm the identity of the killer.