Detective Chan rushes to the hospital to be with his daughter as she prepares to give birth to his first grandchild. While Charlie Chan waits at the hospital, his "number two" son Jimmy intercepts a message intended for Charlie about a murder on board the freighter Susan B. Jennings.
The freighter is on its way from Shanghai to Honolulu under the leadership of Captain Johnson (Robert Barrat). Jimmy wants to prove his investigative skills to his father and so boards the Jennings pretending to be Charlie Chan, with his younger brother Tommy (Layne Tom Jr.) in tow. The ruse doesn't last long and soon the real Chan arrives on board, interrogating a motley assortment of crooks, heiresses and crew as he works to solve a crime whose only witness is secretary Judy Haynes (Phyllis Brooks).