- "You saw one of my skulls, didn't you? Oh yes, I know you did. It belonged to a neighbor of yours. The name was Knapp. We took the house from them. I offered to buy it but you know how old people are, they grow so attached to things."
- ―Werner Klopek to Ray Patterson about the Knapps.
The Knapps were an old couple on Mayfield Place. They were killed by the Klopeks.
The Knapps were never seen in the film, because they "moved" before the events of the film took place.
They were first mentioned when Art and Ray were talking about the oddities of the Klopeks in Ray's garage. Ray brings up the Knapps, claiming to have had two conversations with them all the years they lived next door to each other. However, Art claims that they at least worked in their yard and appeared normal, arguing that the Klopeks are never seen outside.
At the end of the film, Werner reveals to Ray that he killed the Knapps, taking credit for their murders after claiming that they turned down his offer to buy the house. He presumably burned the bodies and buried the bones in the backyard. It is likely that the femur that Art discovered belonged to one of the Knapps.