10 Best "Everything You Know Is A Lie" Moments In Horror Movies

10. Jason's Mother Is The Killer - Friday The 13th

For almost the entirety of Friday the 13th's runtime, the film's ill-fated teenage camp counselors believe that they're being picked off by a back-from-the-dead Jason Voorhees, who drowned at Camp Crystal Lake as a child decades prior.

We as audience members similarly believe this, but at the very end of the movie protagonist Alice (Adrienne King) learns that Jason is indeed still dead, and the person carrying out the killings has been his psychotic, vengeful mother Pamela (Betsy Palmer).

Pamela reveals that Jason drowned because the camp counselors were having sex rather than looking after him, and then drops any attempt to conceal the fact that she's the murderer.

It's a genuinely shocking moment for both Alice and viewers, that what was laid out as an incredibly straight-forward slasher film had a nasty little sting in its tail, of a mother driven to murderous madness by her rage-fuelled grief.

Starting with the second film, though, the series indeed deferred to the more expected mode of Jason indeed returning from the grave and slaughtering nubile youngsters en masse.