The first book of the tetralogy, the Four Mysteries. In a secret cave, hidden among the winter-frozen waterfalls, five young friends open an old trunk and release a story that for many years had been locked up and forgotten. A mystery surrounds the past of someone who claimed to be a brave captain, and Vanilla, Pervinca and the entire Captain's Gang will have to discover the truth about William Talbooth. A few clues, unexpected discoveries and brief memories will help the kids put together the pieces of a buried past that at times appears dark and even scary. However, the image that will slowly form before the amazed eyes of the twins and their companions seems to have the eyes and smile of love.