Adventures of Kitty O'Day (1945)

Kitty O'Day (Jean Parker) is a switchboard operator at a busy hotel where her boyfriend, Johnny (Peter Cookson), also works. Suspicious about some strange noises, she sends Johnny to her employer's apartment, where Johnny finds the boss has been murdered. Kitty is determined to find the culprit, but the hotheaded Inspector Clancy (Tim Ryan) is also on the case, and, as more bodies pile up at the hotel, the police start to throw accusations at Kitty and her amateur crime-solving crew.