Billy and Mandy are sent to "Winter Camp", where they meet Nergal's son, Nergal Jr. Just like his father, Junior tries making friends, although not in the best way possible. Junior attacks the campers, freezes them and, using his shape-shifting abilities, takes over their appearances. Billy decides to be Junior's friend, but he is scared away at the moment Junior shows him his true form.

When Irwin lacks the courage to ask Mandy to go with him to the Valentine's Day school dance, he tells Nergal Jr. to do it for him. Mandy mistakes Junior's invitation for his own, and surprisingly accepts to go with him, which naturally makes Irwin jealous. With the ill advice received from his father, to be possessive with Mandy, at the dance Junior becomes overprotective of her, that eventually he and Irwin start fighting, throwing punch at each other and ruining the ball. It is revealed that this was Mandy's true intention all along so that no one could enjoy Valentine's Day.