Superior 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

Superior Plot Summary and Synopsis

When Marian is on the run, she goes to the only place she knows is safe: her childhood home. She is greeted by her estranged sister, Vivian, a stay-at-home housewife struggling to conceive and on the verge of a failing marriage. Though the two are identical twins, they live opposite lives. Marian’s mysterious return disrupts Vivian’s small-town routine, and the sisters must learn to reconnect and reconcile. When Marian’s haunting past finally catches up to her, their separate worlds collide, catapulting both sisters into grave danger.

Source: Wikipedia (CC BY-SA 3.0).