The action takes place in the San Franciscan Hotel Mardena. A man is found dead in Room 940. It's a room that's not his own and the death turns out to be murder by poisoning. The case gets taken on jointly by McCabe the house detective and resident murder mystery writer Blackwood. Although they are ostensibly acting together there is a rivalry between them in which each other tries to take the other for a fool.
Edmund Lowe plays Blackwood. He is in lots of 1930s and 1940s mysteries. If you like him in this you may also like him as the writer David Chase in the 'Front Page Detective' TV series (1951-1953). I enjoy watching him as an older and tougher character in those episodes. The TV series ran at the same time as the pulp magazine 'Front Page Detective' which must have been a popular read for mystery fans at that time.
Bruiser Victor McLaglen plays McCabe who has a sidekick called Feets played by John Wray. Feets becomes more involved in the story towards the end and provides good knockabout sequences with McCabe. Suspicion passes between a number of characters in party hats at a New Years gathering. The reveal comes in the final scene and then there is an abrupt ending.