Two young girls are out trick-and-treating and knock at the door of a house. They get no answer until the owner, Miss Turner, comes up behind them and jokingly startles them. Miss Turner invites them inside. The girls find three witches performing an occult ceremony in the living room. When the girls try to back out, Miss Turner holds them in place with a spell and begins chanting as well. The lead witch, Robbie Collins, writes in a book in her own blood and tells Miss Turner that her former boyfriend, Brian, chose a life with another woman. Now she plans to even the score and make Brian and his friends rot in hell. The girls step forward and Robbie marks their foreheads with blood. She gives them a book with the circle on the cover and tells them that it won’t hurt a bit. However, the girls scream as black tendrils grow out of the floor and surround them.
Brian and his wife Lisa are at a cabin in the Maine woods and preparing for a relaxing weekend alone. She assures him that she knows it’s been tough on him and they start to kiss. Someone knocks at the door and Brian goes to answer it. It’s Brian’s agent, Anita, who asks if his editor George Clayton is there. Lisa explains that George called on the cell phone and said he’s coming with Kate, his publisher. Anita goes to the bathroom and Lisa explains that she thought she’d get Brian’s agent, publisher, and editor all together to help him.
The five people gather in the living room and Anita talks about Brian’s best-selling first novel, Blood Thirsty
, which he wrote under the pen name Robert Collins. She wants to know when the next book is coming. George objects, saying that his boss understands, but Anita insists that they need a new book from Brian. Lisa says that Brian needed some time to rediscover who he is, but Anita says that it’s time he needs to get back to work. Brian objects, figuring that they want the money, but Anita says that she’s supported him from the beginning. She assures Brian that he’s talented, and he admits that he can’t sleep.
Kate asks how it started, but before Brian can answer, there’s a knock on the door at 9:45. Lisa says that she didn’t invite anyone else and everyone hesitates. Anita finally goes to the door and finds the two trick-or-treat girls They offer Anita the book and she takes it, and then looks up to discover that they’ve vanished. The group looks at the book, titled The Circle
, and Anita figures that Lisa and Brian set the whole thing up as a Halloween prank to introduce his new book. Brian’s pen name is on the book, but he insists that he didn’t write it. Anita starts reading the book, which describes what Brian is going through now and how a group of the protagonist’s friends gathered on Halloween. The book continues, saying that no one was prepared for what was to happen that night.
Brian tries to stop Anita from reading further, and then accuses them of playing a prank to get him to start writing. The others deny it and Anita keeps reading. The book talks about how the circle didn’t recognize the power of the book, but that they soon would when a suffocating darkness settled around the cabin forever, trapping them inside. George goes to the door and sees a cloud of blackness rising around the cabin. The others join him and George goes outside to the edge of darkness. The others beg him to come inside, and a tendril of darkness extrudes itself, grabbing George and pulling it into itself while splattering on Kate.
Kate tries run out after George but the others pull her inside and close the door, just as a tendril of darkness slams against the cabin. Anita tells Kate to calm down and Brian checks to see if any of the darkness got on her. They check their cell phones but Lisa warns them that they’ve never gotten reception. The cabin shakes as the darkness slams into it, and Brian realizes that the story in the book is coming to pass. Lisa starts reading again and comes to the section about how the man’s literary creation came to life and killed the editor. Brian realizes that his novel Blood Thirsty
, which contains a similar creature, is happening for real.
Before he can continue, George appears outside the window. He claws at the window, spewing black goo, and Brian tells them to get back. The writer tells the others that once the darkness takes a victim, they become overcome with a thirst for blood. Lisa suggests that they can use light to drive off the darkness, but Anita insists that it’s nothing but fiction. Kate, sobbing, says that it isn’t anymore and collapses.
The darkness starts oozing in beneath the door and Brian hastily blocks it with a blanket. Lisa and Anita get what they can to block the other windows while Kate panics in a corner. However, the darkness is able to enter through the smallest gap so Brian starts gathering all the light sources that he can and put them in front of the windows. Kate tells them that it doesn’t matter what they do because their fates have already been decided. Anita reads the book and discovers that Kate is echoing the words in the book even though she’s never read it. Kate then tells them that they need to burn the book and picks it up. Before anyone can stop her, she throws it into the fireplace but they discover that it doesn’t burn. When Brian tries to pull it out with a poker, the poker first goes through it. The book then disappears and reappears on the table.
Brian stares at the book and says that “she” cursed it, and Lisa suggests that they read the end and find out what happened. The story concludes by saying that everything went back to the way it began at 9:45. Kate collapses, sobbing, and starts vomiting up black goo. Brian warns that she’s turning into one of the blood thirsty, just like in her book. They realize that a drop of the liquid darkness got into her mouth, and that’s how the infection spread. Kate then rears up and goes for Anita, but Brian calls it over and has Lisa get a flashlight. They get more flashlights and train it on Kate, forcing her back into the bathroom. Brian is forced to kick her in and Kate grabs his foot. Lisa drives her back with the light and Anita locks the doors. Brian is covered in the liquid darkness but confirms that none of it got into him.
Anita wonders what will happen to Kate, and Brian warns that the darkness infects its victims and then devours them from within. He warns Lisa and Anita that they’ll never get to the car in time, and that it reaches for miles. While they talk, Anita realizes that some of the darkness got on her head and she instinctively wipes it off. Brian says that the creatures can be killed like anyone else, but Lisa hesitates to kill their friend. When Anita offers to do so, Brian hands her the knife but she hesitates as well. He tells them that the creature will dissolve at sunlight, but they’ll never survive that long.
Brian gets an idea and suggests that he rewrite the story and change the ending. Anita insists that it’s an insane idea but Brian says that they don’t have a choice. They hear a cracking noise and go to discover that Kate has broken out of the bathroom. The three survivors take refuge in another room and lock the door, and Kate eventually stops pounding on the door. Brian says that he has to go get the book, figuring the lights will disorient Kate. The lights go out and Brian tells them to make fire from the furniture so they can hold out until sunrise. Grabbing a cane as a weapon, Brian opens the door and goes out. He uses a flashlight to make his way to the living room, but Kate grabs him from behind.
Lisa hears Brian’s screams and then someone walking to the door. She tells Anita that they have to get out and turns to her friend, only to discover that she’s become one of the blood thirsty as well. As Anita attacks her, Brian runs in and beats her to death. He then turns to Lisa, the blackness crawling over his features and inside his eyes. Brian leads Lisa out past Kate’s corpse and warns her that he doesn’t have long until he is transformed as well. He has Lisa tie him to a chair and bring him the book, but he worries that he can’t do it. Lisa has him concentrate, reminding him that the book said he would find his muse. Concentrating, Brian gets an idea and tries to write, only to discover that the pen isn’t working. They discover that the book can’t be written in, and Brian realizes that the original words were written in blood and that’s how she brought the curse to life. Lisa asks who “she” is, and Brian starts to explain.
Before he can begin, someone knocks at the door. Lisa goes to answer it, ignoring Brian’s objections. Robbie grabs her and holds a knife to her throat. Brian tells Robbie to let Lisa go, but Robbie asks what he thought of the book and explains that she wrote it just for him. Robbie says that she got tired of waiting for Brian to live up to his end of the deal so she decided to destroy his world. Brian says that he’ll do whatever he wants and Robbie tells Lisa that he’ll leave her. Robbie throws Lisa to the ground and says that she loved Brian. She then wrote Blood Thirsty
, making Brian famous. However, he refused to leave Lisa like he promised because he loved her. As Robbie teases Lisa with the knife, she grabs a poker and knocks her out.
Lisa goes to Brian and he says that he was trying to escape Robbie and make their life better. Disgusted, Lisa gives him the pen and tells him to finish the book. Robbie recovers consciousness and attacks her, while Brian tries to rewrite the story using his own blood. The cabin starts to shake and Brian struggles against the darkness within. Lisa manages to grab the knife and drive it into Robbie’s chest, and then goes to Brian. She realizes that the darkness has killed him, and reads the last few words of the book. It says the same thing over and over, that everything returned to what it was at 9:45 that night when the trick-or-treaters arrived at the cabin. The cabin shakes as the darkness forces its way in while the possessed Brian rips himself free and attacks Lisa.
There’s a knock on the door at 9:45. Lisa says that she didn’t invite anyone else and everyone hesitates. Anita finally goes to the door and finds the two trick-or-treat girls They offer Anita the book and she takes it, and then looks up to discover that they’ve vanished.
And the circle repeats itself over... and over... and over.