Imaginary Friend is a psychological horror novel written by Stephen Chbosky. The story follows a seven-year-old boy named Christopher who goes missing in the woods for six days. When he returns, he claims to have been taken by a mysterious figure known as the Nice Man, who has given him a mission to build a treehouse in the woods. As Christopher becomes more obsessed with completing the treehouse, his behavior becomes increasingly erratic and violent, leading his mother to question the true nature of the Nice Man and his influence on her son.