Mr. Moto (Peter Lorre) investigates a murder during a boxing match, with unwanted help from Charlie's Chan's "Number One Son" Lee (Keye Luke). Most people probably know this, but originally this was intended to be a Charlie Chan film. But when troubled Chan star Warner Oland walked off the set, they reworked the story and turned it into a Moto movie. This explains the appearance of Lee Chan. It also explains why Mr. Moto is less edgy than in his first two films. Here he resemble a more traditional detective like Charlie Chan.
While I love Charlie Chan, Peter Lorre is kind of wasted in this type of role. He's better suited to roles with a little menace to them. Keye Luke is fine but the chemistry and rapport he had with Warner Oland is missing. Also appearing are Harold Huber, Douglas Fowley, and beautiful Lynn Bari -- each no stranger to the Charlie Chan series. In addition, there's Ward Bond, George E. Stone, and Maxie Rosenbloom. Lon Chaney, Jr. has a small part. Given the troubled backstory behind the movie, I'm surprised it turns out as well as it does. But a good cast goes a long way with these old detective movies.