Jack Hughes is a 16 year old orphan. His only inheritance is a 30 foot sailboat and he intends to sail it down the Intra Coastal Waterway from Baltimore to Miami in memory of his recently killed parents who loved to sail. He is joined by a 16 year old girl who has run away from home and wants to forget her home life. They rescue a young boy in Chesapeake Bar and are led to searching for the boy's parents' killers all the way to Cuba. On the way there is a kidnapping and a rescue by the Coast Guard, the two are trained as spies, taught to use weapons, and are given disguises and new identities. They are assigned to work with the security service of Castro's communist country.