Two 18-year-old students elope on the eve of high-school graduation and move in with his parents.
Buzzy Pringle is preparing to graduate from high school when he elopes with his long-time girlfriend, Rosemary Cotts. Both are eighteen years old, although Rosemary still has another year of high school. Buzzy's parents, Jeff and Carol Pringle, and his older sister Elizabeth are stunned at the news. The family nanny takes it in stride. Rosemary's father is dead and her mother is in Afghanistan doing an anthropological study. During her mother's absence she has been staying with the Anderson family.
In the fall, Rosemary and Buzzy plan to move away so he can attend college. Rosemary will transfer to the high school there if she can achieve a passing grade in French. In the meantime, they set up housekeeping in Buzzy's parents' home. Among Rosemary's belongings is a huge stuffed pink rabbit.
Jeff and Carol gradually accept the situation and do their best to make Rosemary feel at home. Mrs. Cotts sends a wedding gift of an African god, which Rosemary insists on displaying in her in-laws' living room.
Elizabeth is to be married soon. Her fiance, Freddy, is very obnoxious and makes rude comments to Buzzy; usually addressing him as sonny boy. Rosemary is jealous because Freddy can afford to take Elizabeth to Hawaii on their honeymoon.
Buzzy has a summer job in his father's company. He does not know that his salary is actually paid by his father. He is very controlling of Rosemary and will not allow her to get a job. She is soon bored and they quarrel. Among other things, she is angry that he drills her in French in front of his parents.
The African god is nicknamed Benny. He is a perverse god, meaning people ask him for the opposite of what they really want. Elizabeth and Freddy are going to a dinner held in their honor. Tired of his future son-in-law's constant bragging, Jeff asks Benny to make sure Freddy never makes a mistake in his schedule. The young couple soon return, embarrassed because the dinner was actually next week. Buzzy makes a few snide comments and Freddy tells him the truth about where his salary is coming from. Buzzy is so angry that he quits on the spot. Rosemary tries to talk over the problem but he tells her to stay out of it. Jeff accidentally pushes Freddy and he falls to the floor. He accuses Jeff of doing it on purpose. Elizabeth is upset and drives Freddy home.
Rosemary goes to bed in tears and Buzzy storms off. He returns hours later with the news that he has gotten a job at a gas station. When he goes upstairs to tell Rosemary, she is gone. She left a note explaining that she has gone back to the Andersons. Buzzy wants to go after her but Jeff tells him to wait until morning.
Freddy's arm was hurting him so badly that Elizabeth drove him to the hospital. The arm is not broken but he is given a sling. They decide to call off their marriage. Buzzy has a nightmare that Rosemary has become a stripper. Meanwhile, Carol is furious with Jeff, blaming him for the breaking up of the two couples. She locks him out of the bedroom. Buzzy and Elizabeth come to him for advice. Instead of returning to his bedroom, Buzzy heads over to the Andersons.
The next morning, a police officer arrive with Buzzy in tow. The Andersons are out of town and Buzzy was arrested for trying to break into their house. All is explained but the family are now worried about Rosemary. Freddy comes over and he and Elizabeth reconcile. Just as the officer is taking down a description of Rosemary, she arrives to collect her belongings. She spent the night with a girlfriend. At first she does not want to reconcile with Buzzy, but he tells her they are moving into a residential motel next to the gas station. It is better for them to be on their own. As they drive away, Jeff realizes that his bedroom door does not lock. He could swear that Benny winked at him.
