While the couple seem happy on surface level, there’s undeniably tension. We learn this has been caused by Natalie having an affair with a friend, and the couple are in counselling in an attempt to work through it. Their counselor suggests a change in environment could be just what they need, so Kevin suggests they buy the house he has just cleaned (yes, the murder house). It’s actually Jay’s sister Claudia sells the house to the couple, much to the displeasure of her husband, Robert).
While Natalie is hesitant at first, she eventually gives in and the pair move in. Not long after, they begin experiencing paranormal activity, noticing that objects appear to be disappearing and reappearing in random places, and their dog barking at an empty closet — all the usual tropes. After being attacked by a mysterious man, Natalie reports the incidents to the police, but the whole ordeal is put down to stress. Eventually though, things get more sinister.
Natalie’s sister Dani somehow disappears in the house, and their dog then has to be put down after ingesting poison. To try and understand what’s going on, Natalie pays a visit to Claudia (the woman who sold them the house). She explains that Jay and Erin were also having marriage troubles, with Jay cheating on his wife with a number of different women. As revenge, Erin started having an affair with a mystery man.
Claudia reveals that she doesn’t believe her brother really killed himself, but is cut off by her husband Robert before she can explain further. Robert offers to buy the house back from Natalie at a reduced rate, but she refuses.
The weird events continue, with Kevin eventually being hospitalised after finding a potentially lethal dose of poison in his bloodstream. The police believe Natalie is trying to poison him, but after she’s attacked by a stranger who tries to sexually assault her, the truth is finally revealed.
They find out that the stranger had come to the house after seeing an advert online, where Natalie apparently claimed that she wanted to be attacked. They find out that Robert (Claudia’s strange husband) had actually posted the advert. He’s severely in debt and needs the house for money, so he attempts to scare them into leaving. He does, however, deny poisoning their dog and attacking Natalie, which turns out to be true.
While home alone one night, Natalie is attacked again by a tall, thin man, who it turns out has been living in the house the entire time. He takes her to a secret basement, where he reveals himself to be Erin’s lover, Otto. He had been living in a space behind the closet door (which Erin designed for him when planning the house). He was waiting to begin his life with Erin, but when she decided to stay with her husband, he snapped and killed them both.
After Natalie and Kevin moved in, Otto began a new obsession with Natalie, and was attempting to kill off everyone around her. Natalie manages to escape by breaking her own wrist, before stabbing Otto to death with a pair of scissors. Unsurprisingly, after the entire ordeal, they finally decide it's time to leave the house.
As with all great horror movies, though, it ends in a twist. The final shot of the movie shows the closet door slowly closing, implying either that Otto isn’t actually dead, or that somebody else has moved in.
Aftermath is available now to watch on Netflix.