Lorna Markham and Scotti Wheeler are best friends who couldn’t be more different at 14-years-old. Lorna is a star swimmer, relaxed and affable, who can eat like a horse and never gain a pound, and who falls dead asleep at 9:30. Scotti is the literary type who sits up half the night working on her novel--she loves sweets but can’t afford them.
If they didn’t know better, Lorna and Scotti would suspect that they were switched at birth. Scotti’s parents are health nuts who live on lemon grass and protein drinks, and wish Scotti would get out and exercise more. Lorna envies the independence they allow Scotti, the maid that means no chores for Scotti, and the privacy Scotti gets from being an only child. Scotti loves everything Lorna’s mother cooks, and appreciates her interest in Scotti’s literary aspirations. Finally the girls come up with a scheme to trade families, and convince their parents with the story that they want to be exchange students, but have to practice by living with another family.
At first, the girls are in heaven. Mrs. Markham cooks Scotti’s favorite dinner. Lorna relishes the peace and quiet of the Wheeler home. But then the adjustment period begins.
Scotti can’t seem to get any work done on her novel. Lorna’s six-year-old sister Tiffy wants Scotti’s constant attention, and Scotti can’t stand Lorna’s noisy, harassing seventeen-year-old brother David--until she develops a mad crush on him! Lorna starts to miss her mother’s waffles and meatloaf, and a strange intruder in the shrubbery turns out to be the gardener, but only after he scares her half to death.
Everyone is excited for Scotti when she manages to get an interview with a big New York publisher who is coming to town looking for new authors. But in Lorna’s opinion, her own mother is a little too excited. When the Wheelers find out about a company trip to Hawaii the same weekend, Scotti wouldn’t dream of going and missing her big break, but she isn’t really very happy about Lorna going along instead.
The spate of confused adventures that follow convince both Scotti and Lorna that living with the other’s family requires more adaptation than they thought. In the end both girls are glad to be back home with their own families, and both moms have a new appreciation of their daughters. No longer convinced that the other one has it made, Lorna and Scotti come to be better friends than ever.