Mr. Burns train ride back to Springfield from Yale is interrupted by an obstacle on the tracks. While the train sits, a man named Larry hawks souvenirs to the passengers. When he sees Mr. Burns, his jaw drops in surprise, and he packs up his gear to follow the train to Springfield.

The Simpsons see Larry hitchhiking to town and stop to pick him up. In Springfield, Larry heads to Mr. Burns's estate and identifies himself as Burns's long-lost son. Burns, acknowledging the resemblance, admits that Larry is the result of a one-night fling during a college reunion.

At first, Burns accepts his son, but tires of him when Larry proves to be an incurable oaf. However, Homer befriends Larry, realizing that they share many of the same interests. They fake Larry's kidnapping to help Larry win back his father's love. Marge convinces Homer and Larry to abandonm their plan, but as they leave to confess their scheme to Mr. Burns, they are chased by reporters and police. Burns forgives Larry for the hoax, but explains that he cannot continue as his father. Announcing that he is returning home, Larry stages an impromptu street party.