Harriet Wermer is unhappy about having to spend her summer with her grandmother on Marble island until she discovers a mystery involving her Dad from when he was a boy living on the island.

As far as twelve-year-old Odette Zyskowski is concerned, her parents have ruined her life by selling the house she and her younger brother have grown up in, getting an RV, and giving her some little mutt instead of the Labrador Retriever she wanted--but as they travel north to see her grandmother, Odette becomes aware of an even more frightening problem: her parents may be on the verge of a divorce.