Horror films often deal with viewers' deepest fears and the intrusion of evil forces into everyday life. They attract large audiences by exploring the dark side of existence. Two plot ideas presented are: 1) A group of friends unleash an evil spirit during a Ouija board session at a sleepover that kills them one by one as they hide. 2) A couple investigating a reportedly haunted asylum encounter malevolent spirits and meet tragic ends as they try to escape. Key elements like creepy sounds, dim lighting, and suspenseful editing are discussed for an effective horror film trailer.