The Hardys have agreed to sail a friend's yacht from the island of Saint Martin to the coast of Florida. But sinister winds are blowing across the Caribbean, and the brothers' voyage is about to take a deadly detour. In the middle of the night, a 5,000-ton cargo ship appears out of the darkness and nearly sends the yacht -- and the boys -- to the bottom of the sea.

When Frank and Joe investigate, they discover that the freighter's crew is missing and that they've landed in a shipload of trouble. The ship's secret cargo may have incited a mutiny and may soon ignite the violent overthrow of an island nation. From Puerto Rico to Panama, the boys pursue a gang of black marketeers willing to sell anything -- including human life -- for a price!