It is best remembered for originating as a movie in the Charlie Chan series and being changed to a Mr. Moto entry at the last minute.

In San Francisco, policeman Lieutenant Riggs (Harold Huber) takes Mr. Moto, a detective and Lee Chan (Keye Luke), a student, to a prizefight between Bill Steele (Dick Baldwin) and Frank Stanton (Russ Clark), where the winner will take on the champion, Biff Moran (Ward Bond).

However, the fight is fixed and gangster Nick Crowder (Douglas Fowley) bets big money that Stanton won't make it to the fifth round.

In March 1938, Fox announced Oland would return to the role and appear in Charlie Chan on the Clipper Ship.

[7] Lee Chan is Moto's student in his criminology class at San Francisco University.

[10] Filming finished late March 1938, the fourth movie shot in the Moto series.