The story is based on the allegedly haunted dybbuk box. Bornedal cited films like The Exorcist as an inspiration, praising their subtlety.
A newly separated couple Clyde Brenek (Jeffrey Dean Morgan) and Stephanie (Kyra Sedgwick) live in different homes. After Clyde picks up their two children, Emily "Em" (Natasha Calis) and Hannah (Madison Davenport), for the weekend, they stop at a yard sale where Em becomes intrigued by an old wooden box that has Hebrew letters engraved on it. Clyde buys the box for Em, and they later find that there seems no way to open it. That night, Em hears whispering coming from the box. She is able to open it, and finds a tooth, a dead moth, a wooden figurine, and a ring, which she begins to wear. Em becomes solitary, and her behavior becomes increasingly sinister; she stabs her father in the hand with a fork during breakfast. That night, the house, especially Em's bedroom, becomes infested with moths.
At school, Em violently attacks a classmate when he takes her box, resulting in a meeting with Clyde, Stephanie, the principal and the teacher. Em's teacher recommends that she spend time away from the box, so it is left in the classroom. That night, curious about the mysterious noises from the box, the teacher tries to open it, but a malevolent force, the dybbuk, murders her by violently throwing her out a window. Em tells Clyde about an invisible hag who lives in her box who says that Em is "special". Alarmed by her behavior, Clyde attempts to dispose of the box. During their next weekend at Clyde's, Emily gets progressively more upset with the disappearance of the box. She begins yelling at Clyde in the hall with Hannah watching in the back. The dybbuk seems to slap Em across the face. She begins yelling, asking why he's hitting her, from Hannah's perspective it looks like her father actually does. Em flees the house, recovers the box and the dybbuk begins conversing with her in a strange language.
Clyde takes the box to a university professor who tells him that it is a dybbuk box that dates back to the 1920s; it was used to contain a dybbuk, a dislocated spirit as powerful as a devil. Clyde enters Em's room and reads Psalm 91; a dark but invisible force throws the Tanakh across the room. Clyde then travels to a Hasidic community in Brooklyn and learns from a Jewish priest named Tzadok (Matisyahu) that the possession has three main stages; in the third stage, the dybbuk latches onto its human host, becoming one entity with it. The only way to defeat the dybbuk is to lock it back inside the box via a forced ritual. Upon further examination on the box, Tzadok learns that the dybbuk's name is "Abyzou", or the "Taker of Children".
Em has a seizure and is taken to the hospital for an MRI. During the procedure, Stephanie and Hannah are horrified when they see the dybbuk's face in the MRI scans next to Em's heart. Clyde and Tzadok join the family at the hospital and attempt to conduct an exorcism. Where Em is taken to a room that has a tub full of water and a stretcher to keep Em stable during the exorcism. During the exorcism, the possessed Em attacks Tzadok. Clyde grabs Em from him, and Em runs out of the room. Clyde follows her out and finally finds her in the morgue where the lights are off. As he nears her, she starts to attack him. Clyde survives the attack, but the dybbuk is passed from Em to him. Tzadok performs a successful exorcism; Abyzou emerges from Clyde and crawls back into the box. The family is reunited, with Clyde and Stephanie's love rekindled. Tzadok drives away with the box in Clyde's vehicle. The car is hit by a truck, killing him. The box lands safely from the wreckage, and Abyzou's whispering is heard from it, the same Polish rhyme heard at the beginning of the film.
The film was shot in early 2011.
Bornedal stated that he was drawn to The Possession's script, having seen it as more of an allegory for divorce than as a true horror film. Actors Sedgwick and Morgan were brought in to play the Breneks; Morgan chose to participate after seeing Calis' audition tape. Parts of the movie were filmed at a former mental institution, Riverview Hospital in Coquitlam, British Columbia.
The owner of the dybbuk box, Jason Haxton, offered to send it to producer Sam Raimi, who was both interested and reluctant. Raimi laughingly told an Entertainment Weekly interviewer, "I didn't want anything to do with it. I'm scared of the thing." He also told the interviewer that he was raised in a conservative Jewish home: "You don't hear about dybbuks when you go to synagogue. I know the demonic lore of The Exorcist. But what does my faith believe about demonic possession? ... The stories chilled me to the bone." Jeffrey Dean Morgan felt similarly: "In the research I did, I started getting creeped out. My girlfriend was like, 'Let's just make sure that we don't actually go near the real Dybbuk Box.'"
"We were like, 'Hell, no,'" recalls screenwriter Juliet Snowden. "'We don't want to see it. Don't send us a picture of it.'"
Director Ole Bornedal said, "Some really weird things happened. I've never stood underneath a neon light before that wasn't lit, that all of a sudden exploded. The worst thing was, five days after we wrapped the movie, all the props burned. This storage house in Vancouver burned down to the ground, and the fire department does not know the cause. I'm not a superstitious man, and I would like to say, 'Yeah, it's just a coincidence.'"
The film has received mixed reviews from critics. It currently holds a rating of 41% on Rotten Tomatoes based on 91 reviews. The general consensus states, "It may be based on a true story, but that doesn't excuse the way The Possession repeatedly falls back on hoary ghost movie clichés – or the unintentional laughs it provides." On Metacritic, the film holds a score of 45/100, indicating "mixed or average reviews", based on scores from 26 critics.
However, Roger Ebert gave the film 3½ stars, writing "The Exorcist has influenced a lot of films, and [The Possession] is one of the better ones." Richard Roeper also gave the movie a B+.
The film ranked #1 in its opening weekend, taking in an estimated $17.7 million, and an estimated $21.3 million for the full Labor Day Weekend.