A scientist working on cures for rare afflictions, such as a bone softening agent made from molds to allow him to correct the spinal deformity of his nurse, finds the physical causes of lycanthropy in wolf-man Larry Talbot and of vampirism in Count Dracula, but himself becomes afflicted with homicidal madness while exchanging blood with Dracula.

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.