A young artist gets stranded in an extensive, immaculate forest in western Ireland, where, after finding shelter, she becomes trapped alongside three strangers, stalked by mysterious creatures each night.
This forest isn't charted on any map. Every car breaks down at its treeline. Mina's is no different. Left stranded, she is forced into the dark woodland only to find a woman shouting, urging Mina to run to a concrete bunker. As the door slams behind her, the building is besieged by screams. Mina finds herself in a room with a wall of glass, and an electric light that activates at nightfall, when the Watchers come above ground. These creatures emerge to observe their captive humans and terrible things happen to anyone who doesn't reach the bunker in time.
Mina, a pet shop employee carrying the wounds of a troubled past, finds herself stranded in a mysterious forest in Ireland. As night falls, she seeks shelter, only to become entangled in a hair-raising conspiracy. Now trapped inside a decaying woodland shelter with three perfect strangers, Mina is unaware that unseen creatures watch their every move with keen interest. Separated from the eerie unknown by a gleaming, one-way mirror and a strict survival procedure, the group is always in grave danger. When resistance is futile, can the confined specimens outwit their captors and escape the Watchers' grasp?—Nick Riganas
The film begins with a man wandering through a forest. He becomes lost and is eventually pulled underground, seemingly meeting his demise. Meanwhile, in a pet shop in Galway, an American named Mina is asked to deliver a golden conjure parrot to a zoo near Belfast. On her journey, Mina's car breaks down in a forest. As she searches for help, she encounters a bunker and a woman who urges her to get inside if she values her life.
This woman, Madeline, resides in "The Coop" with Ciara and Daniel. As night falls, they gather in front of the Coop's mirrored window for "The Watchers." Madeline informs Mina that the Watchers will enjoy meeting her and assures her safety as long as she follows the rules: the Watchers kill anyone outside the Coop at night, and nobody is to enter the Burrows, the underground tunnels where the Watchers hide during the day due to their aversion to sunlight.
The group has been trapped in the forest for several months. Ciara's husband, John, left the Coop days ago and has not returned. Daniel helps Mina explore one of the Burrows, where they find items like a camcorder and a bicycle, and narrowly escape a Watcher. That night, John appears outside the Coop, but Madeline refuses to let him in, convinced he is a Watcher imitating John. In anger, the Watchers crack the mirror. Madeline returns the items to the Burrow to appease them.
As winter sets in, tensions rise within the group. One night, Daniel locks Mina and Madeline out of the Coop, forcing them to seek shelter in the forest. There, they witness the Watchers-humanoid creatures that mimic the Coop's occupants-and realize the Watchers react angrily to their absence. They manage to return to the Coop, where Madeline explains that the Watchers are shape shifting fairies trying to better mimic humans.
The Watchers attack the Coop, forcing the group to retreat through a hidden door to an underground study. There, Mina finds video diaries of Professor Rory Kilmartin, who had come to the forest to study the fairies. He captured one and bonded with it, but his final entry shows him despondent, explaining how to escape the forest and asking for his research to be destroyed. He then shoots his captive and himself.
The next day, following the professor's directions, the group reaches a river at the edge of the forest. Madeline shows them a stone marker where the fairies were imprisoned without their wings after a war with humans. A Watcher imitating John kills Daniel, and the rest escape using the professor's boat.
Mina later visits the professor's university office to destroy his notes. She learns that humans and fairies once coexisted peacefully, with some hybrid offspring that could withstand daylight. She is shocked to discover that Madeline resembles the professor's wife, who died in 2001, realizing Madeline is a fairy.
At Ciara's home, they are attacked by Madeline, who explains she was outcast by the Watchers for her ability to endure sunlight. Mina persuades Madeline to spare her life by revealing she is half-human. She urges Madeline to let go of her hatred towards humans and seek out other hybrids. Madeline sprouts wings and flies away.
In the end, Mina reconciles with her estranged twin sister, revealing that Madeline is now a guardian for her. The film concludes with Madeline, in the form of a young girl, blending into a crowd.
