The book, Door To December, is a suspenseful novel. Dean Koontz does a remarkable job in explaining the detailed events of the story. The story is about a little girl named Melanie who was kidnapped by her father at the age of three. During her time with her father, Melanie was subjected to tortures beyond imagination. The story takes place the morning of three brutal murders at the house where Melanie and her father were residing. Melanie's mother, Laura, had just been notified of the homicides and had arrived at the house. There, a police officer named Dan Haldane informed her of what had happened. He also told her that a girl, around the age of nine, had been found wandering the streets nude and oblivious to world around. Melanie's mother told the officer to take her immediately to the place where she was after they were finished at the house. While there Melanie's mother identified her brutalized husband and toured the house until she came to the Gray Room. This room was filled with a sensory deprivation chamber, an electric chair, and other forms of torture.
After the house, Laura went to the place where Melanie was and was reunited with her. One thing was wrong though, Melanie was in an autistic, almost catatonic state. From there, Laura, Dan, Melanie and a bodygaurd named Earl, search for the truth behind Melanie's lost past. Along the way, they are being chased by an invisible creature that has been committing all of these murders. They soon find that the answers to this troubling mystery lies within the unknown Door to December.