I did a search on YouTube for 1940s films and found this.
Boris Karloff plays a Chinese detective (yep) called Mr. Wong, who does all the sleuthing and catches the murderer. His partner in law is a short-tempered cop who gets things done, but is not good at detecting. Mr. Wong is described as a Chinese-American, but has a right proper British accent.
At one hour and six minutes it is short by today’s standards, but it packs a good story in, no fluff or time wasting here. The editing was a bit abrupt at times though.
At one point in the film there were people being bumped off every few seconds and the short-tempered cop was going nuts while Mr. Wong was cool, collected, and figuring stuff out. Quite funny to watch.
Jason Robards Sr. had a part in this. Junior would have been 18 at the time.
There is a sequel to this called Doomed To Die which I will check out soon.
Date watched: May 22nd
Film count 2016: 85