Domenica Santolina Doone, known as Dinnie, has spent most of her life traveling around the United States because her father is transiently employed. Dinnie feels that she has settled into this routine of never having a permanent home until one night, her whole world changes. With her older brother in the Air Force after ending up in jail again, her sixteen-year-old sister pregnant and married, and her dad still on the road for yet another home, Dinnie is taken away by her maternal aunt and her husband to Switzerland, where Uncle Max (her uncle) is the new headmaster of an international boarding school.
Dinnie becomes a student at the school, where she makes friends, sees new, exciting things, and has many adventures of her own. She befriends a girl named Lila, who at first seems nice but then starts complaining a lot, but Dinnie still really likes her. Dinnie also has a friend named Guthrie, a spontaneous and fun-loving "fantastico!" person. She also gets to know Keisuke and Belen, a Japanese boy and a Spanish girl, who love each other but their parents are not supportive of their relationship. The group is later joined by an Italian girl named Mari. During a Ski trip with the boarding school, Lila and Guthrie get trapped in an avalanche and are saved because Dinnie watched where they fell and was thus able to locate them. Both of them survived and made a full recovery.
Interspersed in the novel are Dinnie's diary entries, postcards from her two paternal aunts informing Dinnie of what is happening with her family, and Dinnie's various attempts to communicate to the local community using signs at her window that she wants to return home. However, as the year progresses, Dinnie begins to thrive in the diverse environment and the stability of remaining in one place. At the end of the year, Dinnie's aunt and uncle give her a choice: Go home to America for the summer and come back to school in the fall, or go back to America permanently. It is never said what her decision was, but Dinnie keeps her skis in the closet so that she will have to come back someday.