Professor William Waterman Sherman, tired of teaching arithmetic, sets off in a hot-air balloon for a year of peaceful solitude. Instead of drifting quietly over the Pacific, he crash-lands on the secret volcanic island of Krakatoa, which is populated by wealthy families living in extraordinary luxury. The island's society is built on a remarkable secret—a diamond mine—and is organized with fantastic inventions and a unique calendar system. The professor's adventure becomes a thrilling tale of discovery, ingenuity, and a spectacular escape when the volcano threatens to destroy everything.