The Return of Doctor X (1939)

New York newspaper reporter Walter Barnett finds himself out of a job after he claims to have found actress Angela Merrova dead in her apartment - only the next day she showed up alive and threatened to sue the paper. Determined to investigate he discovers her involvement with a strange doctor who is an expert on human blood. Barnett then finds a connection to a series of gruesome murders where the victims were all found drained of blood.