When Jupiter Jones, Pete Crenshaw, and Bob Andrews talk their way into a meeting with famous film director Alfred Hitchcock, they ask him to introduce their first case to help launch their new detective agency. Mr. Hitchcock, agrees, but only if they can find him a haunted house for his next movie.
Jupiter decides Terror Castle is the perfect place for Mr. Hitchcock's movie. It was the home of movie star Stephen Terrill, who died in a car accident many years ago. Terrill is rumored to haunt his former home to keep anyone else from living there.
During their investigations, the three boys find very scary and seemingly real activities going on in the abandoned structure, such as a fog that induces fear and a blue phantom.