Is the sacrifice of an innocent life to save the world justified? The question has played out in many famous works of art, a play on the Christ archetype that discomfitingly forces audiences to consider how far they’d be willing to take utilitarian logic of the trolley problem. Knock at the Cabin explores that question with an interesting twist: A family must pick a sacrificial lamb from among their ranks, and the chosen one must voluntarily die. It is not enough for a death to occur—the deceased must choose it.
Eric (Jonathan Groff) and Andrew (Ben Aldridge) are a gay couple vacationing at a remote cabin with their adopted 7-year-old daughter, Wen (Kristen Cui). While playing in the nearby woods, Wen is approached by Leonard (Dave Bautista), an enormous man who says he wants to be her friend and that he is there to help her family make a difficult decision. Three other strangers walk out of the woods, the family is tied up when they try to resist, and eventually Leonard explains that the foursome is there to prevent the apocalypse. They were all chosen, he says, and experienced shared visions of the end of times and, more importantly, how to avoid it: By coming to this cabin and convincing Eric, Andrew, and Wen to select a member of their family to kill.