The Cuckoo - Season 1

In episode one, at a farmhouse under renovation, Jessica is interviewing potential lodgers to relieve her family's financial strain. Fourteen-year-old Alice, who has a difficult relationship with her mother, is against the idea. Jessica begins to lose hope until Sian, an artist, arrives. Their conversation is interrupted by their plumber's wife, demanding payment for work, leaving Jessica embarrassed. Sian offers to cover the bills with her deposit.
Nick and Alice return home and are introduced to their new lodger. Sian is charming but Alice is uncomfortable and Nick voices his concerns to Jessica about taking so much money from Sian.

Later, Jessica admits to Sian that she struggles to connect with Alice, and that Nick had an affair. Nick contacts one of Sian's references, discovering Fay Calder is her aunt, heightening his suspicions. Nick expresses his doubts about Sian but Jessica dismisses him.

In Alice's bedroom, she is drawing as Sian enters and they bond over their love of art. Sian encourages Alice to embrace her talent. Nick makes a desperate call to a business colleague for a loan while Sian eavesdrops. He opens a safe hidden behind a family photo, takes out valuable jewellery…

At school, Ottilie and a group of girls taunt Alice, snatching her sketchbook. Later, tensions rise between Nick and Sian. He asks Sian to leave their house, offering to repay her deposit. Sian questions his motives and insinuates that he has sexual feelings for her. Jessica and Alice return home as a jar smashes in the kitchen. They find Sian cleaning up with a flustered Nick nearby…

Sian's arrival has already started to destabilise the family…

Sian lies in bed contemplating a distant memory. Nick announces he's fixed the shower to save money, irking Jessica. He shuns Sian's offer to drive Alice to school.

Sian guesses the safe's combination and takes out a slip of paper. Jessica approaches Sian about disclosing Nick's infidelity and Sian casually hands her the slip revealing a pawnshop receipt. Nick, sensing something is wrong, checks the safe. He confronts Sian about the receipt but she stonewalls him as the phone rings. It's Alice's headmaster who explains she's been in an altercation. Sian listens as Alice opens up about her difficulties with her parents. They see Alice's school bully Ottilie, and Sian frightens her off.

Jessica and Nick discuss the pawning of her mother's jewellery and how the slip got out of the safe. The frostiness between Jessica and Nick intensifies when they discuss Alice's behaviour before meeting the headmaster.

Sian visits her Aunt Fay and admits that she knows a dark secret Nick and Jessica are keeping from Alice, as Fay pleads with her not to do anything extreme. Jessica and Nick try to talk to Alice before she explodes and storms out, taking the family car. Sian chases after her with Jessica. They catch up with Alice but witness her crash into a ditch. Sian and Jessica check on Alice who seeks Sian's comfort.

Jessica and Nick discuss the hospital visit and getting the car towed. Sian tries to advise Jessica, who admits her concerns about being a mother. Alice discloses to Sian that she wants to leave…

Alice becomes the centre of Sian's manipulations...

Alice wakes up in a state of confusion. Jessica wants to give her space as Sian suggested, so leaves to let the school know Alice won't be in, as Nick storms off to collect the car.

Sian lies to Alice about her parents not caring for her. Jessica sees Nick pull up in a hire car and they argue about the cost.

Fay is left reeling at the news that Sian wants to bring Alice to her house and they argue about family history. Fay asks her to leave. Sian pockets a key as she goes.

Jessica attempts to speak to Alice who initially refuses but eventually opens up. Alice is combative and an argument begins between the two, with Alice calling for Sian's help. Sian asks to speak with Nick alone where she claims that he is jealous of her closeness with Alice. As Nick protests, Sian begins to hit her head against a photograph on the wall.

Police officers arrive having gotten a call about a disturbance. Sian falsely claims Nick hit her and they arrest him as Jessica watches on. Nick is helpless at the police station. Jessica tries to reconcile with her daughter but Alice feels the family is broken. Jessica catches Sian trying to access the safe. She confronts Sian and throws her out.

Jessica tries to contact the police station. She becomes suspicious of noises in the house and questions Alice. Nick tries to call Jessica but can't get through. Suddenly, Alice appears in the hallway flanked by Sian…

The drama builds to a deadly conclusion...

Sian is overjoyed as they drive but Alice is unsettled. Jessica breaks out of the cupboard informing Nick, who has arrived home, of Alice's kidnapping. Nick and Jessica track Alice's phone location. At a service station, Alice tries to send a message but Sian catches her and dumps her phone. Nick and Jessica arrive too late and discover that Alice was trying to send Jessica a text. They race to Aunt Fay's - their only clue to Alice's whereabouts.

Sian takes Alice to a desolate caravan park and reveals that this is where she came to have her baby, explaining that she didn't want to go to a hospital due to fear of losing custody.

Jessica and Nick arrive at the caravan park and start searching. They find Alice near a cliff edge. Jessica tries to reason with Sian, telling her that Alice isn't her daughter. Sian seems to grasp the truth but then charges at Jessica. In the struggle, Alice is pulled free by Jessica just as Sian drops off the cliff. They glance over but her body is gone…