Mr Moto cross overs into the Charlie Chan universe.
A boxer dies in the ring, it is later found that he was poisoned, the poison being found on the gloves of his opponent Bill Steele (Dick Baldwin), the death was to fix the fight so gangster Nick Crowder (Douglas Fowley) could make a ton of cash out of the bookies. Japanese detective Mr Moto (Peter Lorre) proves the boxer's death was murder but the search goes on to find out who was behind it.
Meanwhile Lee / Number One Son (Keye Luke) is attending a class by Mr Moto and in his bumbling way gets involved in the investigation... not that Mr Moto really needs any help.
This is a decent detective story, more sedate than Mr Moto adventures often are... more like a Charlie Chan story indeed. That is because this was supposed to be a Charlie Chan film but Warner Oland died early in the film's production and so the film was rewritten to be a Mr Moto film. But it does mean that Mr Moto and Charlie Chan did solve crimes at the same time if we want to get all modern day movie universe about it, it is just a shame of course they didn't get to meet.