Allison has a dream of her driving the car during her graduation night and running over Lennon. The dream makes it seem like she saw Lennon in the road and purposely ran her over. Dylan in the dream wanted to go home.

Allison's mother is back in town to claim the cult's bible after Clara's death. She thinks "Lennon" would choose to live with her and join the cult.

Allison confides in Margot that she thinks Dylan could be the killer. She manipulates her last confrontation with Dylan to be about him believing she's "Allison" instead of her telling him the truth.

Dylan tells Lyla the truth about Allison pretending to Lennon and them killing "Allison" during the hit-and-run. Lyla doesn't believe him because she and Bruce think Dylan has been stalking "Lennon" in the black truck. Lyla needs proof from him, but he only thinks Margot could prove it.

Allison confirms to Bruce that Margot doesn't suspect anything. Bruce took care of their Dylan problem.

Lyla visits Margot to ask her about "Allison's" suicide. Margot's mom calls Bruce to give him the heads-up that Lyla came to visit them.

Margot is freaking out about Dylan going to the police. Allison doesn't reveal to Margot that she slept with her. However, Margot finds the used condom in Allison's bathroom.

Lyla tells Bruce that she doesn't believe Dylan's story.

Margot asks Dylan if he slept with "Lennon." He admits that they had sex and that Allison told him the truth. Margot thinks that Allison and Bruce killed everyone; all the deaths were people who could tell the difference between the twins. Margot gives him Allison's computer to hack into to see if she has the killer videos. Margot is going to try to get a confession from "Lennon."

Lyla and Bruce have sex. Lyla wonders how "Lennon" will react once she and Bruce get engaged.

Allison's mother knows immediately that she's alive. She reveals that she missed the cult and wanted to be with them; she left to be with Fred. Allison's mother says that there's something wrong inside of Allison.

A flashback shows Allison and Lennon arguing at the party; she wished Lennon would be gone forever. It's confirmed that Allison purposely drove into Lennon on the highway.

Margot secretly records her conversation with "Lennon." Allison doesn't give her the information she needs to frame her.

Allison's mother Helen can't find the bible at the compound; she chastises him and Allison for what they do for the Lennon lie. Bruce promises to find the missing cult bible.

Margot tells Dylan she knows that Allison's mother is in town. They want to find her so that she can reveal the truth to the police. Dylan is pulling out the brain from a dead animal; he places it in a jar with the same spiders from the cult.

Margot visits Clara's house in search of Helen. She heads into the basement to find a dead animal body.

Allison is scared because she hears mysterious noises in the house. Dylan has broken in and told her that he "freed" Clara for her better next life. Allison knows that Dylan wrote her the threatening note. Margot calls them both to come to find her.

Lyla gives her medical examiner photos of both Lennon and Allison to determine which twin is which.

Dylan and Allison find Helen's bloody dead body in Clara's basement. Someone knocks out Dylan. Allison follows the sounds of Margot's crying tears in the distance; there are photos from the cult along the path.

Margot is revealed to have killed Helen; she did it for the pain caused to Lennon.  Margot knew she was Allison all along because of the social media posts when she left for school. Margot stabs Allison.

Bruce calls Margot's mother to look for Allison.

Kyle places a dead body in the trunk of a car.

Margot questions Allison about all her secrets and why she kept the Lennon lie going. Allison tries to keep the lie going; Margot doesn't believe her.

A flashback of the car crash shows Margot caring for Allison.

Allison says that she cares about Margot and wants to help her like how Margot helped her. Margot reveals her plan was to frame Allison for all the murders and get her locked up, but she can't live knowing that Allison is out there keeping the Lennon lie.

Dylan wakes up locked in a room at the compound.

Margot confirms that Allison is Allison because Lennon would never apologize.

Dylan breaks free and tries to stop Allison from bleeding out. Margot plans to frame Dylan for killing "Lennon." Dylan takes Margot's gun away, but as he points the gun, Lyla arrives to break up the situation.

Margot manipulates Allison into claiming Dylan was the killer and was the one who attacked them in the basement.

Helen's body is missing from the basement. Kyle has taken the body to the caves.

Dylan keeps claiming that Helen is dead, that Margot placed his DNA on "Lennon," and Margot is the killer. Bruce keeps the lie going by claiming Helen has been dead for years and that Lennon is alive.

Margot tells Allison that she loves her and can't believe she would frame Dylan. The police find Lennon's computer, the arctic spiders, and Riley's severed arm at Dylan's house.

The medical examiner confirms that the photo of "Allison" is similar to the dead body they found in the ocean. A flashback shows that Bruce switched the photos he had of Allison and Lennon on his desk.

Allison lies to Bruce that she doesn't know what happened to Helen.

Scenes show Dylan being placed in jail, him reading the cult bible to the prisoners, the police placing Riley's severed hand in jail, and Allison agreeing to never leave Margot.

Riley's eyes open in the frozen.