Lisa is a demonic ghostly shape who was thought to be an imaginary friend of a little girl named Amy, who documented their time together in her diary. She taken Lisa to school where Amy tries to present Lisa for show and tell, resulting her getting into trouble with the teacher, Miss.Monroe. The next day Miss.Monroe is not present and the class has a substitute named Miss. Dickman, is is more kinder and patient with the narrator.
As the story progresses Amy gets into trouble with her father because she and Lisa went out for a walk so late at night. He coldly tells her that Lisa is fake, and then Lisa disappears. The next day Amy writes how Miss. Dickman will be their permanent teacher because Miss.Monroe hasn't come back yet. She also tells how her father hasn't come home from work in two days.
Amy reunites with Lisa who tells her everything is OK, and that her father and teacher are now "Sleeping with Lisa's daddy", implying that Amy's father and teacher have been killed.