What is the importance of Levy Castle in the novel, The Agathas?

Levy Castle is a Registered Historic Landmark in Castle Cove that once belonged to Brooke's family. Her grandmother had lived in the castle when she was young, but her father had lost his fortune and the castle. The castle is used annually for the Main's big Halloween party. Alice goes to the party uninvited and fights with both Steve and Brooke before leaving and going home. Park tries to drug Brooke so she can have a chance at hooking up with Steve, but Steve gets drugged instead and starts a fight with Brooke, who runs into the woods outside the castle. It is there, just yards away from her friends at the party, that Brooke runs into Ms. Westmacott.