Dick tries to experience youth for the first time by partying with his students during spring break, but his drunken antics are wasted on Mary, who is trying to relive a favorite, and more relaxing, family outing. Meanwhile, Don and the police have moved into the Solomons' apartment in order to survey a video pirate living opposite. Sally is hugely turned on when she sees Don ordering his fellows about, but he is emasculated when tough government agent Jack McMannus arrives and takes over the operation, and Sally becomes attracted to him.

The Big Giant Head has revealed to Dick that he is his father, and so would like to get to know his girlfriend Mary better; however, Mary gets drunk at the dinner party and reveals that she has slept with over forty men in her lifetime. The Big Giant Head orders Dick to break up with Mary so he decides to run away with her, before Tommy reminds him that Earth children defy their parents all the time. Meanwhile, Vicki invites Harry's new girlfriend Janice to Tommy's graduation, where she attempts to kill her from beneath the bleachers; however, Sally quickly realizes what's going on and rushes to intervene before it is too late. The time comes for Tommy's speech, but he puts aside talking about his achievements to try to convince Alissa to forgive him.

Dick and Mary decide to go on a double date with Sally and Don, but things start to become uncomfortable when Dick and Sally begin talking incessantly about how good their other half is in bed. The next day Dick and Sally come to realize that neither Mary or Don said anything about how good they are, and immediately worry that they aren't. Meanwhile, in a food store, Mary and Don run into each other and, consumed by what they'd heard about each other in bed, share a kiss. Elsewhere, Harry and Tommy follow in the footsteps of Jack Kerouac and take to the open road.

Mary's mother Martha arrives in town and Dick decides to tell her what Mary really thinks of her - that she ruined her childhood. Angry, Martha tries to attack Dick and falls over, ending up in hospital. When Dick goes to visit, however, Martha tells him her side of the story, and a deeply moved Dick takes her side and promises to tend to her during her recovery. Meanwhile, Harry and Sally get a nasty surprise when throwing junk in the time space portal - a new alien.