On school holidays at the wild, sunlit edges of Kiabuntu Game Reserve, siblings James and Charlotte team up with friends Sipho and Tassia, and a mischievous meerkat named Kato—for a sail that turns into a mystery. What are those rough men doing, slipping into the cliffs where a waterfall seems to vanish inside the mountain? Kato leads the way as the kids uncover hidden passages, trapdoors, and a maze of sea caves that test their courage and cleverness.

Deep underground, the beam of a headlamp lands on the impossible: a centuries-old Spanish galleon sealed inside the rock, its secrets whispering from the dark. But treasure isn’t all they’ve stumbled upon—Joe and Albert will do anything to keep their smuggling scheme from being exposed. Now the friends must outthink the villains, brave the stormy coast, and follow the clues before the tide and the bad guys close in.