Complex sentence: She is very intrigued about the discovery, so she shares it with Principal Skinner, but when she brings along the school newspaper, they only find what is supposed to be behind the door, the "Banned Band Books".
Split into simpler sentences: She is very intrigued about the discovery, so she shares it with Principal Skinner. But when she brings along the school newspaper, they only find what is supposed to be behind the door, the "Banned Band Books".