Jessica, a sly, 16-year-old sitter outfoxes the boys while Lois is away and Hal's busy with a second job as a whiz of a salesman.

Malcolm and Reese plot revenge after they realize their teenage neighbor has tricked each of them into believing the other is gay. Meanwhile, Hal, tired of competing with a neighbor who always outdoes his Christmas decorations, decides to create his own "holiday" to decorate his house for - Pearl Harbor Day.

When Jessica goes through some family troubles, Lois agrees to let her stay at the house, making the boys crazy.

When Malcolm gets paired with a dimwitted beauty as his chemistry partner, he thinks it's a recipe for disaster, but when she reveals her feelings for him, sparks fly. They agree to keep their romantic experiment under wraps until Malcolm realizes that she's just embarrassed to be dating him. Meanwhile, Lois demands that Reese get a job, and she kicks him out of the house to prove that she means business.