Keenan ends up living with his father on an island that is part Canada and part US when he is diagnosed with tuberculosis. He got the disease in his travels with his mother, who flits from country to county, and being in Canada is both restful and boring, especially since he is not allowed to do anything but sit in a lawn chair. Things become less boring when he meets ZaraBeth, who likes to be called ZeeBee. She is obsessed with gangsters from the 1930s, and all of their activities with Prohibition. She is also sure that her dog, Barney, was murdered. This suspicion has merit-- Barney was a huge dog who wreaked havoc on the island, tearing up gardens, damaging property, and stealing food from stores. ZeeBee has another dog, a small, fluffy pooch called Barney Two, but she wants nothing to do with him. The two have a good summer, but when Keenan starts school on the island and ZeeBee has to take a ferry to the Canadian school, she is upset when he starts to hang out with other kids, who think that ZeeBee is a little weird because of her dog and her gangster obsession. The other kids aren't perfect, and at one point trash the local lighthouse. Keenan wants to stay friends with ZeeBee, so helps her to investigate Barney's death, and in doing so, comes across information that leads to the unraveling of a Prohibition Era mystery as well.