The Return of Doctor X (1939)

When news reporter Walter Garrett arrives at the hotel room of bombshell actress Angela Merrova to conduct an interview, he finds her dead from multiple stab wounds. He returns with the police to find the hotel empty and the body vanished. Garrett writes about the incident but is fired when Merrova, alive and well, goes to the paper to complain. Now his only chance to get his job back is to find the truth, which involves the grisly scheme of a madman.