The Stairs Ending Explained [SPOILER!]

SPOILER ALERT: the following article contains massive spoilers, including the ending. If you have not yet seen the movie, proceed at your own risk, or better, come back to this article later!

SPOILERS AHEAD

The Stairs Plot Summary and Synopsis

A frightening tale about a group of hikers hunted by a sinister presence in the woods. Twenty years after the mysterious disappearance of an 11-year-old boy and his grandfather, a group of friends find themselves along the same trail, unaware of a long-forgotten evil lurking just beyond the tree line. What started as a week-long adventure with friends, quickly turns into a terrifying fight for survival as they come face to face with the thing that nightmares are made of.

Source: Wikipedia (CC BY-SA 3.0).