Plot

The story of a therapy group that is forced to confront the monsters of their past when an isolated weekend retreat tests their emotional resilience and ability to survive.

Joy lives with her abusive boyfriend Derek. One night, he attempts to strangle her, but she fends him off and locks herself in a room. She comes out of the room to find that he has killed her dog.

Six months later, Joy has left Derek. Her long-time friend Carmen invites her on a retreat in the woods with her therapist Dr. Dunnley to help her deal with her trauma, which she accepts. Joy and Carmen travel with another patient Tara to meet Dunnley and Shaina. While travelling through the forest, Joy and Shaina discuss their respective traumas. That night, Joy experiences nightmares involving Derek and a monstrous creature.

The next day, when she and Carmen are performing a trust exercise in the forest, Joy hears Derek calling her name. She confronts Dunnley about whether they are lost. Joy later admits to Carmen that she heard Derek, which Carmen expresses doubt about, since she didn't hear anything. Around the same time, Tara becomes separated from Shaina while performing the same exercise, and hallucinates her hands being bound and bloody. After Joy finds her, she notes that she also experienced hallucinations.

While the group is walking through a cavern, Joy experiences auditory hallucinations. In the forest, Joy and Carmen are briefly separated while Joy is relieving herself. She sees Derek and the creature again, and an unseen force starts strangling her. Carmen finds her and brings her back to camp. Joy has become convinced that something is following them. That night, she experiences nightmares again.

Upon waking up the next day, the group realises that Tara has gone missing, and their supplies have vanished. While looking for Tara, Dunnley also experiences hallucinations, and goes missing as well. Joy and Carmen try and fail to persuade Shaina that they should go to get help. Shaina tries to look for Dunnley and Tara, but falls off a rock while experiencing hallucinations of her time as a soldier in Afghanistan. Joy and Carmen are unable to find her body.

While looking for the others, Joy and Carmen come across a cave, and find Tara inside it. Carmen tries to save Dunnley, but she is killed by the creature. Joy, Carmen and Tara hide from it in a cluster of logs in a nearby river, but it finds them. Tara sacrifices herself to allow Joy and Carmen to escape. They make it back to the camp to treat Carmen's leg injury.

Joy admits that she saw Derek the day they left for the retreat. It is revealed that she knocked him out in self-defense after letting him into her house. That night, the creature kidnaps Carmen, forcing Joy to return to the cave to save her. Joy sees the creature as Derek, and briefly embraces it before stabbing it and setting it on fire with Derek's lighter. She and Carmen escape from the cave with heavy injuries, and set out for a hospital. (thanks to Wikipedia)