I've seen hundreds of old mysteries, and most turn out to be silly detective yarns where you know who the killer is from the start. This is a well-written exception where the clues gradually lead to the revelation of the killer at the end. Any of a variety of characters in a hospital could be the killer. The script balances suspense, drama, and humor to lead through some interesting plot twists to the inevitable conclusion. This film was a Crime Club selection. Bruce Cabot is probably best known as Driscoll in King Kong. Coincidentally Frank Reicher had a role in that too.