Obviously, we’re going to have to talk about some ending details, so here’s your second spoiler warning. Don’t read if you haven’t seen the movie yet!
In the book, the young daughter, Wen, is accidentally killed during a struggle with a gun leaving just her grieving two dads to figure out if the hostage takers are right that the world is ending unless they make the conscious choice to kill one or the other. Wen doesn’t count, you see, because it wasn’t a willing sacrifice. They ultimately choose that whatever life looks like after their experience at the cabin. Apocalypse or not, they’re going to face it together and we never know if the world ends or not.
The ambiguity is kind of the point of the book, which is mostly a battle of wills between the logical victims and the creepy intruders who fully believe they’re there for the best of mankind, but let’s be honest … they give off super culty vibes. The movie throws out that ambiguity and definitively answers the question of whether or not these intruders are the Four Horsemen of the Apocalypse by having the protagonists make the sacrifice to appease whatever angry god is forcing this scenario and leaving the other to raise their daughter in the now-saved world.