After successfully thwarting a dastardly plan to steal rare marine animals, Ben and Fee MacTavish feel they can relax and continue learning all about nautical life on board School Ship Tobermory. But it's not long before their everyday routine is interrupted by an extraordinary event. The crew find themselves embroiled in another adventure that leads them to a small island in the Caribbean, where they learn about Captain Macbeth's past and come face to face with modern-day pirates.