Slim and Tubby are American cops in London to study police tactics. They wind up in jail and are bailed out by Dr. Jekyll. Jekyll has been murdering fellow doctors who laugh at his experiments. He has more murders in mind. At one point the serum that turns Jekyll into the murderous Hyde gets injected into Tubby. Starring Bud Abbott, Lou Costello, and Boris Karloff. One of the later Abbott and Costello comedies and Karloff is good in this one.
