Boris Karloff spent a good chunk of the early 1940s playing mad scientists in films like The Ape (1940), Before I Hang (1940), The Man with Nine Lives (1940), The Devil Commands (1941) and The Boogie Man Will Get You (1942). He’ started in this mode in in 1936 with The Invisible Ray but despite a couple of similar roles, it was really the 1940s when he really embraced him inner deranged doctors. For Universal, he made Black Friday for director Arthur Lubin, an uneasy mix of Warner Bros. style gangster film and the mad scientist film which doesn’t really work as either, but which is, in its own unassuming way, affable enough.

Karloff plays Dr Ernest Sovac who we first meet being see being executed in the electric chair for crimes as yet unknown. On his way to his fate, he gives a reporter a set of notes outlining his ghastly deeds and the story unfolds in flashback. We learn that his scholarly friend, college professor George Kingsley (Stanley Ridges), has been badly injured in a traffic accident (on Friday the 13th, hence the title) when he’s run down by a car driven by mobster Red Cannon (also played by Ridges) who is fleeing his mutinous gang. In order to save Kingsley’s life, Sovac implants part of Cannon’s brain into the professor’s head. As he slowly recovers, Kingsley begins displaying character traits associated with Cannon and Sovac, learning of Cannon’s $500,000 stash, hopes that he can prompt Kingsley to “remember” where it is. But Cannon somehow manages to assume control of Kingsley’s body, physically transforming into the gangster who then sets about taking revenge on his former gangmates, now led by Eric Marnay (Bela Lugosi).

The script was written by Universal’s go-to writer in the early 40s, Curt Siodmak who had some form when it came to brain transplants – in 1942, he’d published the novel Donovan’s Brain which would later be adapted for radio by Orson Welles as an episode of the series Suspense, and three times for the big screen, as The Lady and the Monster (1944), Donovan’s Brain (1953), and Vengeance/The Brain (1962). Unfortunately, his grasp of how the brain actually works is shaky in the extreme. There’s little point in trying to sort out how his transplant procedure works, how it leads to Kingsley’s physical transformation (the film owes as much to the various adaptations of Jekyll and Hyde as it does anything else), nor where his consciousness goes to when Cannon is in charge. It’s not the sort of film overly concerned with such niceties so trying to make any sense of it is a fool’s game.

So the script isn’t up to much and there’s more disappointment for fans of Karloff and Lugosi, teamed here for the fifth and final time in a Universal horror. Despite sharing top billing, the two never actually meet. To make matters worse, Lugosi never really convinces as a tough, New York mobster, but then he was never intended to be. During pre-production, Lugosi was set to play Sovac, a role more suited to him, while Karloff was to have played Kingsley/Cannon. Virtually at the last minute, Karloff was recast as Sovac, Ridges was brought in as Kingsley/Cannon and poor Lugosi was relegated to a rather thankless supporting role.

The result leaves Lugosi little to do but wander about in a hat and suit being menacing while Karloff gets to refine the mad scientist role that he was soon to be doing an awful lot of. Anne Nagel is stuck with an equally “nothing” female lead, playing Sovac’s daughter, which leaves the bulk of the heavy lifting to Ridges and thankfully he’s more than up to the job at hand, handling the mousey Kingsley and the sadistic, vengeful Cannon with equal aplomb. He effortlessly steals the show from his starrier cast mates and the film is frequently at its best when he’s doing his on screen – his first transformation, Kingsley lowering his head into his hands and coming back up as Cannon is a simple effect, one almost as old as cinema itself, but its neatly done.

Lubin had made his debut at Universal in 1936 with the crime thriller Yellowstone and earned himself a reputation as a swift worker. He stayed at Universal until the 1955 historical drama Lady Godiva tanked at the box office, and was closely associated with Abbott and Costello, as well as making Phantom of the Opera in 1943, Ali Baba and the Forty Thieves the following year and the Basil Rathbone Sherlock Holmes “sort of” spin-off The Spider Woman Strikes Back in 1946, a film he wasn’t particularly keen on, and one can hardly blame him. He seemed happier making a series of films featuring Francis the Talking Mule, six of them in all between 1950 and 1955 before overseeing a small screen variation on the same theme, Mister Ed (1961-1966). On Black Friday, he makes a good stab at the early film noir look and brings some occasional pizzazz to the proceedings.

Black Friday has a poor reputation, but it’s not really all that bad. It’s a bit ordinary, a bit routine, but it’s entertaining enough if you don’t think too hard about the many plot holes and inconsistencies. Lugosi fans are going to feel short-changed, understandably so, but Karloff is good value and Ridges is excellent. Its meagre budget (it cost just $137,000 – £2.7 million in today’s money) occasionally shows through, with its use of stock footage and recycled musical cues, but the pacing is good, and it rattles along at such speed that you barely notice most of its inconsistencies while they’re happening.