Twelve-year-old Sam is convinced that his parents plan to have Pogo, their elderly and infirm Labrador retriever, put down. To save Pogo, Sam sets sail with the dog on a fourteen-foot catboat, heading for an island off the coast of Maine. The elements conspire against them as they move from one danger to another: blinding fog, lurking sharks, a gathering storm. Sam summons unimaginable courage and admirable ingenuity to meet each challenge, helped along the way by Pogo's loyalty, a one-eyed cormorant, a retired ornithologist and a lifetime of good nautical advice from his older brother.