Black Friday is a 1940 American horror film starring Boris Karloff and Bela Lugosi. Screenwriter Curt Siodmak would revisit this theme again in Donovan's Brain (1953) and Hauser's Memory (1970). Plot Dr. Ernest Sovac is taken from his cell for his execution, but is able to give notes to a reporter, which recount his story, as he is led to a chamber. Sometime earlier, Sovac's best friend, bookish college professor George Kingsley, is run down while crossing a street. In order to save his friend's life, Sovac implants part of another man's brain into the professor's. Unfortunately, the other man was a gangster who was involved in the accident and was apparently heading for the electric chair, according to the police. The professor recovers but at times behaves like the gangster. Sovac is horrified but also intrigued, because the gangster has hidden $500,000 somewhere in New York City. The doctor continues to treat his unwitting friend and persuades him to take a vacation in New York; Sovac hopes this will revive the gangster's memory so that Kingsley will lead him to the fortune which he hopes to spend on a laboratory. Unfortunately for the doctor's plans, the professor's personality change becomes more extreme, including plotting revenge against other members of his former gang. When Kingsley (behaving as a gangster) attempts to murder the doctor's daughter, Sovac shoots him dead. Returning to present, Sovac is executed. Cast Boris Karloff as Dr. Ernest Sovac Stanley Ridges as Professor George Kingsley/Red Cannon Bela Lugosi as Eric Marnay Anne Nagel as Sunny Rogers Anne Gwynne as Jean Sovac Virginia Brissac as Mrs. Margaret Kingsley Edmund MacDonald as Frank Miller Paul Fix as William Kane Murray Alper as Bellhop Gonzalo Meroño as Richard Steward Production The original story treatment was titled Friday the Thirteenth before being changed to Black Friday. In January 1939, Universal announced that Willis Cooper was working on the script, with Bela Lugosi and Boris Karloff probably to star. In August, Curt Siodmak and Eric Taylor were assigned to write the script. Universal cast Lugosi as the doctor and Karloff as the professor. For unknown reasons, Karloff insisted on playing the doctor. Rather than a straight switch though, Lugosi was given the minor role of another gangster, while character actor Stanley Ridges was brought in to play the professor. In later years, writer Curt Siodmak claimed Karloff felt he was not a