Roger and the girls return home, he notices Ed is working on the old Chevy and approaches him. Roger explains he was skeptical at first, but thanks him for helping his family. Ed explains that with each case they take, it takes it's toll on Lorraine, draining her a little more each time.
That night, they settle in for more observation. While pouring himself coffee, Brad hears a noise outside. He investigates the back porch and only sees a rocking chair slightly rocking. Once back inside, he see a ghostly woman with slashed wrists dressed as a maid, then she disappears. He looks around when suddenly out of the darkness, the maid charges him, frightening him as he falls back.
A moment later, Cindy begins to sleepwalk again. While walking upstairs, thermal cameras observe a temperature drop around her as she enters into the wardrobe, whereupon the bedroom door slams shut behind her. The others force their way into the room and find a secret passage behind the wardrobe.
After Cindy is taken out, Lorraine enters the wardrobe and falls through the floor boards down into the cellar. There, she sees the spirits of people whom Bathsheba has possessed, and realizes Bathsheba's purpose: to possess mothers and use them to kill their children.
After Lorraine escapes the cellar, something grabs Nancy's hair and is dragging her violently around the room. Ed and Roger try to pin her down, but they are just dragged along with her. Lorraine rushes in with scissors and cuts Nancy's hair, ending the ordeal.
Roger packs up the family to take refuge at a hotel while Ed makes plans for an exorcism. Drew follows the family in his VW van. Sensing something, Lorraine goes out to the boat dock and sees a vision of Judy, their daughter, floating by under water. She rushes back to the house, calls home, and confirms Judy is okay.
Lorraine and Ed take their evidence to Father Gordan to organize an exorcism, the priest agrees to push through approval himself.
The Warrens head back to their own home on a stormy night. We see their daughter, Judy asleep and her gold locket is swinging. She is suddenly woke up when she feels someone tugging at her feet. Judy calls out to her parents and Nanna, the sitter, but no one answers. She explore downstairs and finds the door to the room filled with possessed items, open.
We see that the Annabelle doll is now missing from the glass case. All the lights go out and Judy backs into Ed's den and closes the door. She screams when loud banging persists at her door. Judy turns to see someone in the rocking chair with the Anabelle doll.
The doll's head turns and looks at Judy. She tries to get out, but the door is locked. She looks again, and now the rocking chair is empty. Almost home, Lorraine senses something is wrong. Nanna wakes and rushes to her, but the old lady can't get the door open. Ed and Lorraine charge in as the father forces the door open. At that moment, the rocking chair goes flying in the air about to strike Judy when Ed grabs her just in time. Ed finds Annabelle in the glass case, the cabinet latches/locks still in place.
Back to the Warrens, Roger and Drew return from a grocery run to find out Carolyn is driving back to the house with two of the daughters, Christine and April. After calling Ed, Roger and Drew take off in pursuit.
Brad joins Ed and Lorraine, and they race to the house where they find Roger and Drew struggling with Carolyn as she tries to stab Christine with a pair of scissors.
Once they have confined Carolyn, they plan to take her to the priest, but Bathsheba won't allow her to leave the house. At the front entrance, severe bruising and open sores instantly form on Carolyn. Her body then goes flying back to the cellar where she is thrashed about. Lorraine explains if Carolyn leaves the house, it will kill her. Drew secures Christine in his van and goes looking for April.
In the cellar, the group have their hands full with the possessed Carolyn, like holding down an enraged powerful ape. She's punches, strangles, smacks, and throws them about like rag dolls, then bites a bloody chunk from Brad's cheek. Lorraine throws a sheet over her, allowing the others to pin her down, and they manage to bind her in a chair with rope.
Ed suggests they call the priest, but Lorraine reminds him that the priest is too far away, forcing Ed to perform the exorcism himself. Lorraine retrieves the book and Ed begins the exorcism, including splashing holy water on her. This incites the witch into a raging frenzy, causing everything in the cellar to shake and tremble.
In the van, a bird attacks Christine, breaking the window. Drew still can't find April and he too is attacked by a bird. Soon, numerous birds are invading everywhere, including the cellar. The exorcism continues as it intensifies.
While Ed recites the ritual, Carolyn spits blood from inside the sheet. Roger tries to intervene, but Lorraines pleads to him they are fighting for her soul and Ed persists.
During the chanting, Ed demands the witch to reveal herself, the sheet rips open, revealing Bathsheba. Drew hears April under the floor boards in the kitchen and begins ripping up the floor after he retrieves a crowbar.
Carolyn seemingly stops struggling, and for a brief moment it seems the excorism was successful. Suddenly, her chairs flips over end and she is held upside down. Ed yells for the demon to put her down, and after a few tense moments, she is released onto the ground. After nearly being crushed by a falling cabinet, Ed rushes over to Carolyn and returns to reciting the ritual.
The angered Roger demands the demon to leave his family alone and leave her body. Carolyn slowly turns to Roger and says, "She's already gone." Drew yells down the cellar that he found April, and this alerts the Demon inside Carolyn. She grabs the scissor and dashes through wood tunnels to find April, in order to complete the sacrifice. Ed and Lorraine Warren, along with Roger, rush after her in order to stop her from going through with it.
The possessed Carolyn chases after April thru a tunnel underneath the floorboards. Carolyn grabs a hold of April, and raises the scissors to strike. Ed catches her attention by shouting "Bathsheba!", declaring he condemns her to hell by the power of God. At that moment, Lorraine reaches down through the floor and grabs Carolyn's head.
She tells Carolyn to remember how much her family means to her, to remember what she told her about how special they were to her, that they mean the world to her, and what she would leave behind if she went through with it. This seems to get through to Carolyn, as her face relaxes, and her breathing returns to normal. The demonic presence in her eyes seems to fade, and she puts April down.
The scene changes to Carolyn being helped out of the front door, to a now sunny morning. As she crosses from threshold of the door into the sunlight, the bruises on her skin fade away and she returns to her normal self. Roger and Carolyn rejoice with their family in the front yard, embracing one another, knowing that it's finally over.
The Warrens return to their home. Ed enters his room of possessed objects and artifacts. He places the old music box from the house on an empty space on a shelf. Lorraine enters the room, and they leave together. After a few seconds, the music box starts to play on its own, and the camera slowly pans back to the music box. The camera zooms in on the mirror of the open music box, and the music slowly comes to a stop.
From the script:
The Perron family left the house that day, and never returned. They relocated to Oregon, where they haven’t had anymore encounters. Shortly after their move, the house was purchased by an anonymous buyer, whom Ed and Lorraine believe was the Catholic Church. The Warrens went on to investigate over eight thousand cases, and to this day, Ed is the only non-ordained Demonologist ever recognized by the Vatican. It was one year later that the Warren’s were called to Amityville.