Complex sentence: They are driven to a house in the country, where they discover the identity of the mysterious being behind the kidnappings, who tells the Goodies that he is the Music Master, and he tells them the reason why the kidnappings occurred.
Split into simpler sentences: They are driven to a house in the country, where they discover the identity of the mysterious being behind the kidnappings. Telling the Goodies that he is the Music Master, he explains the reason why the kidnappings occurred.