The film begins at Heathrow Airport, where a Polish immigrant named Lena Malley (Olga Fedori) is working a shift as a cleaner.

Birdie introduces Lena to her adopted brother Elbie (Toby Alexander), who also works at the airport and is a mute.

She wakes up dressed as a child and tied to a chair to the sound of screaming coming from another room.

Moments later, Mum (Dido Miles) and Dad (Perry Benson) enter the room and introduce themselves.

Lena makes an escape attempt but Dad grabs her and Elbie drags her back to the table.

Lena finds and hides a mobile phone but is quickly caught and put on heavier sedation as a consequence.

A few days later Lena catches the attention of a man outside but is seen by Dad, who drags her into his torture room, puts her in a suitcase and orders Elbie to hit it with a hammer.

The following night Lena manages to break free from the restraints of her bedroom while the family is sleeping.

She goes downstairs to find the same man from the attic crucified on the wall, and the mentally ill girl in a chair.

She flees downstairs, followed by Dad, who trips, causing Mum and Birdie to help him.

The woman opens the back door, but Birdie attacks her again, so she hits her over the head with an iron she finds on the floor and rushes outside.