Keenan is bored. He is recovering from tuberculosis, stuck sitting in a lawn chair at his dad's place on Centerlight Island, Michigan, which is divided by the Canada/US border. So he's intrigued when a girl his age, Zarabeth (ZeeBee for short), pops through the garden hedge one day to say hello. ZeeBee lives on the Canadian side of the border and she is still mourning her former dog, Barney, who died six months ago. ZeeBee is full of conspiracy theories, paramount among them that notorious gangster Tommy-Gun Ferguson (original owner of the house she now lives in) buried millions in treasure on the island. Centerlight was apparently a main route for rum runners smuggling liquor from Canada into the U.S. during Prohibition. She is also convinced that Barney was murdered-- he was a large dog that wreaked havoc on most of the island. Keenan doesn't believe either of these theories-- until one day he is walking through the woods near ZeeBee's house and finds a small clearing full of long-dead small mammals, and a piece of what he realizes must be poisoned meat. Maybe Barney was murdered after all! So he sets out to figure out which of Barney's many enemies had both motive and opportunity to do the deed. And when ZeeBee's house is broken into with nothing stolen, they decide that this mystery must be connected with the rumoured treasure-- first, get rid of the guard dog, then break into the house to find the clues. ZeeBee and Keenan finally identify the treasure map, which was hidden in plain sight, and set out to find the missing gold-- but will the dog-murdering criminals find them first?