Architect and happily married man Evan Webber (Keanu Reeves) has the house to himself and his dog Monkey on Father's Day weekend (due to work and a physical therapy appointment due to a shoulder injury) while his wife and children go on a family-planned beach trip. His wife Karen (Ignacia Allamand), a successful artist, leaves their assistant Louis (Aaron Burns) in charge of her sculpture that needs to be moved to an art gallery. Alone in his beautiful and expensive home, Evan works on renderings for an ongoing house project.
That evening, young two women, Genesis (Lorenza Izzo) and Bel (Ana de Armas), arrive and knock on his front door. He opens the door and they say that they are looking for the address of a party, but since their phone died, the taxi driver dropped them off. As they have no means of communication, Evan allows them in to use the Internet and get hold of the party's host. Once they find the right address, Evan offers to call an Uber driver for them, but the closest driver will take 45 minutes to arrive. Meanwhile, the girls make themselves at home and Evan plays a few of his old vinyl records he has from when he was a disc jockey. The conversation quickly turns into their opinions about human polygamy and they tell Evan about their jobs as flight attendants as well as how they engage in sexual activity with a new man in every city they fly to. They then disappear to the bathroom and when their driver finally arrives, a circumspect Evan finds them in the bathroom, naked and lusting for him. Outraged, Evan tries to convince them to leave, but as they start forcing themselves upon him, he gives in and has a threesome with them.
The following day, Evan finds them eating breakfast and watching Family Feud, not worried at all about leaving. He loses his patience and offers to drive them home, since they have not taken the cab. Evan returns indoors only to find out that his wife's sculpture, which Louis was supposed to collect for the art gallery, has been vandalized. When Evan threatens to call the police, the girls reveal they are underage, showing they have control over him or risk charges on sexual conduct with a minor.
Vivian (Colleen Camp), a friend of Karen's, stops by to see if Evan needs help. Seeing Genesis, Vivian angrily leaves, thinking that Evan is cheating on Karen. A shocked Evan tries to make sense of the situation, since he realized that everything the girls had said was a lie in order to get him in bed. When Evan threatens to report a break-in, they give in and agree to be taken home. He drops them off at an upscale neighborhood where they supposedly live.
Evan returns home, cleans the mess, and tries to go back to his work. Just as he is getting closer to completing his project, he hears a shattering noise. He goes looking for the source of the noise as he is supposedly alone indoors. He finds a broken picture-frame of his family and Genesis knocks him out with one of his wife's sculptures.
The two sinister women tie Evan up and go through his family's belongings. Bel climbs onto him trying to arouse him while role-playing as a school girl in his daughter's school uniform. Evan initially refuses, but the girls threaten to FaceTime his wife with him in a compromising position. Even though this disgusts him, Evan realizes that by moving on the bed he can loosen his binds, so he plays along. Bel semi-rapes him, and unbeknownst to him, Genesis records everything.
A few minutes later, Evan finally releases himself where he jumps at Bel and knocks her off. He charges at Genesis, who stabs him in his wounded shoulder with a fork. She then pins him to the ground and both girls proceed to tie him up to a chair with electrical cord.
Later on, Louis arrives to collect the sculpture Karen left him in charge of. The girls take Evan's phone and text Louis saying his niece and her friend are staying over. They hide Evan in a room. Louis enters using his keys. He panics upon finding the vandalized sculpture and immediately realizes these girls are lying about their relation to Evan. Louis then finds Evan tied up to a chair, but before he can help him he hears the girls smashing the vandalized sculpture. He runs to stop them, but then has an asthma attack, and realizes they took his inhaler. The girls play monkey-in-the-middle with his inhaler, and as he tries to get it back, he slips on a piece of the sculpture and knocks his head on the edge, killing him.
Genesis and Bel turn Louis' dead body into a red sculpture and dig a makeshift grave in the backyard meant for Evan. They also reveal to him that they had been spying on him all along for several days now. He fails in his various attempts to make an emergency call and to escape from the house. They tie him up with a hose, then bury him in the hole, leaving only his head above ground. Genesis shows Evan the video she recorded earlier with his phone of him and Bel having sex. As a horrified Evan watches on, she uploads it to his Facebook profile. Ultimately, they spare Evan's life, going against the idea of killing him in the same fashion they had killed Louis.
Revealing that it had all been a "game" and that they're used to tricking fathers into this type of situation, the two sinister women finally depart and take the dog Monkey with them, leaving a broken Evan to his fate in trying to dig himself out of the hole he is buried in while watching the uploaded video with comments coming in. Karen and the kids arrive home to see the entire house ruined. Evan's son says "Daddy had a party" as Karen and the kids remain speechless.