10 Horror Movies You Didn't Know Were Based On True Stories

The Strangers - about a couple who are terrorized at a vacation home by a trio of masked killers - is one of the most effective home-invasion thrillers in recent memory, and it becomes even scarier when you learn that it was based on real-life events.

One inspiration came from an encounter that writer-director Bryan Bertino had when he was a child. He once heard a knock at the door while his parents were away, and upon answering it, he was greeted by some strangers, who asked for someone who didn't live there. Later, Bertino found out that these people were responsible for a series of robberies, and were knocking on people's doors to check if anybody was home.

The Manson Family murders also provided some inspiration for the film, and it's easy to see the parallels here. Four members of the Manson family invaded the home of Roman Polanski and Sharon Tate in 1969, murdering five people before leaving.

The last real-life inspiration behind The Strangers is a little-known case called the Keddie Cabin Murders, which was the quadruple homicide of Susan Sharp and three teenagers who were staying at the Keddie resort with her. To this day, the case remains unsolved, which is possibly where Bertino got the idea to use a gang of faceless, nameless killers from.

All three events are similar in that they involved a group of people invading - or attempting to invade - someone else's home. It's a terrifying thought, and Bertino used that to fuel his chilling, tense script.