It's 1996, and we see a young Cam wearing a Halloween mask sleepwalking into his parents' bedroom. His mother wakes him up and starts to berate him for his behavior. In a fit of anger, Cam knocks her down the stairs, killing her. Well, I guess if you want to be good at something, you start early.
Back in the present, Cam and Sarah are carving a pumpkin and preparing for Halloween aka Sarah's birthday. We have a feeling it's going to be eventful...
Business at the art gallery is booming thanks to Sarah's encounter with the Executioner and the surrounding murders, but hey! A sale is a sale. Robin arrives and invite her to his Halloween party, though Sarah's not super into it.
Alan asks Cam how he's doing after June's death, but he's surprisingly over it (which makes sense, since he killed her). Alan also cautions Cam against getting involved with Sarah too quickly, calling it "unseemly," to which Cam responds by calling out Alan for his own perversions (getting nailed to a cross by a dominatrix, maybe?).
Cam leaves, and Alan is sufficiently suspicious enough to start rummaging through his bedroom where he discovers Cam's box of murder mementos. Come on, Alan. Given that Cam murdered his mother as a kid, you had to see this coming, right?
Alan tells Cam that he knows the truth, and Cam agrees to turn himself into the police and confess everything... Just kidding! He chokes Alan to death. Guess the Executioner wasn't done killing after all.
Dylan writes an article in the paper about how he ruined his marriage because of his obsession with the Executioner, and Sarah begins to consider reconciling with him. That's put to a halt though because Cam has other plans in store...
Cam sneaks into their house and he places his box of murder mementos in one of Dylan's gym bags. Sarah finds it, and she informs the police. Dylan is arrested for the Executioner's murders. Pretty sneaky, Cam.
Cam consoles Sarah, who is perplexed why Dylan would have left the evidence in such an obvious location, but Cam distracts her with his confession of love and some pretty steamy sex.
Cam leaves to interrogate Dylan, and later Sarah discovers an old camp scrapbook. She sees a photo of Cam with a drawing he made. There's something odd about it... she looks closer and realizes that the drawing style is very similar to the Executioner's... oh snap!
Sarah sneaks into Cam's house that night and discovers a bloody basin and knife in the basement, along with a bag of Alan's body parts. Murderer confirmed! She dials 911, but hangs up the call and picks up the knife instead...
Robin is toasting the memory of Justin at his Halloween party right as Sarah arrives. She's looking for Cam, and Robin directs her to his table. She asks to see him outside. What have you got planned, Sarah?
Sarah pulls Cam into a corner and starts kissing him. He's a little thrown off by her forwardness... and his instincts are proven correct when she pulls out his knife and stabs him in the stomach!
At that moment, Robin arrives to see what's going on. Cam musters up the strength to pull out the knife out, and he stabs Robin in the chest! Sarah screams and runs for it.
Sarah arrives back at her house and hides, calling the police. Cam bursts through the door and tries to get into her bedroom. But Dylan, who was freshly released from custody after some finagling from his lawyer, arrives and attacks Cam.
Yet as Cam prepares to make one final stab, Sarah manages to grab the urn of Brenda's ashes nearby and smashes it into Cam's head! Way to go, Sarah! She grabs the knife...
Sarah momentarily considers leaving, but turns around. She wants to finish this for good. Dylan comes down the stairs, and tells her she's not a killer, but she refuses to back down. She asks Dylan to hold Cam down. She stabs Cam in the stomach.
Sarah stabs Cam repeatedly, reminding him of all of the people she has lost due to his murderous ways and telling him he meant nothing to her. As the police arrive, Sarah slices Cam's neck and is sprayed with his blood. Damn.
Four weeks later, Dylan and Sarah are standing outside the house with Robin, who has more lives than a cat, apparently. They are finally leaving the town for good and leaving the past behind. Sarah hugs Robin good-bye, and they drive away to start a new chapter in their lives.
A family with a young daughter arrives at the house, and Robin gives the a tour. The girl walks around the house and notices a cat on the ground. She picks it up and calls it "pretty" before gleefully snapping its neck. She walks inside the house and tells her family the house is "perfect." Uh-oh...