An ill Richie is home alone after the rest of the family go to see Cinerama. When he goes to see what is causing noises downstairs, he finds a burglar.

Fonzie asks Richie to watch after his girl, Denise, while he's out of town at a demolition derby. Denise, upon hearing what Fonzie's asked Richie to do, decides to test Richie's trustworthiness. Richie succumbs to temptation and makes out with Denise at Inspiriation Point, but he later finds out that she has mononucleosis.

Richie, Potsie, and Ralph go on a trip to Chicago with the school choir. Not wanting to stay in their hotel room all night, they decide to sneak out and see a show.