This movie was based on . . .

I see a lot of conjecture here on this Board, in the trivia, and elsewhere. The Manson murders, the Keddie murders, the director's own experience . . .

Actually, I'm pretty sure it was based on Lord of the Rings and Home Alone.

In Lord of the Rings, many people were killed with sharp objects. Also, Liv Tyler.

Home Alone involved several people coming into a house to get other people. Actually just one. But whatever, close enough.