Frankenstein's unscrupulous colleague, Dr. Bohmer, plans to transplant Ygor's brain so he can rule the world using the monster's body, but the plan goes sour when he turns malevolent and goes on a rampage.

Abbot and Costello must find a replacement for a woman's horse they accidentally killed after feeding it some candy. They head for the racetrack, find a look-a-like and take it. They do not realize that the nag is "Tea Biscuit," a champion racehorse.

An American pilot is shot down over Nazi-occupied France and is taken to a convent by the Resistance. The young novice nun Clothilde is interested in him and is willing to help him escape to England, but the pilot must continue his mission undercover by posing as the husband of a different woman.