The film begins with Clare, a young tourist who arrives in vibrant Berlin, Germany. As she navigates her way to her hostel, she immerses herself in the lively atmosphere, celebrating the night away with fellow travelers on the rooftop. Captivated by the sunrise, Clare captures photos and sets out to explore the city the next day, where she indulges in shopping and candid street photography, including a striking moment of a woman hanging colorful sheets from her apartment window.
In her explorations, Clare encounters Andi, who appears quite charming when their paths cross at a bookstore. Their initial conversation begins with a serendipitous incident where Clare helps him pick up his dropped items. When Andi casually offers her strawberries, a connection forms, leading them to a public garden. As they converse, Andi's comment about complicating life prompts Clare to correct him, emphasizing her desire to contemplate life instead.
Despite ignoring a call from her mother, Clare's attraction to Andi grows, culminating in an exhilarating almost-kiss after he drives her back to her hostel. The following day, their paths entwine again at the bookstore, paving the way for more adventures together. Andi's quiet, secluded apartment looms ahead, and Clare expresses her longing to extend her stay instead of moving on to Dusseldorf. However, when morning arrives, Andi must leave for work, revealing his role as a teacher.
Once Clare attempts to depart, she makes a shocking discovery: she's locked inside his apartment, with no spare key available. Assuming it to be a mishap, she remains, crafting meals while awaiting Andi's return. When he arrives, he finds her trapped and playfully teases her about the situation. They embrace with an intimate moment, only to quickly dive deeper into a troubling reality.
As Clare explores the apartment, she stumbles upon unsettling clues, including a picture of her sleeping with the word "mine" scrawled on her shoulder, which ignites her sense of panic. The absence of her heirloom necklace compounds this worrying realization, leading her to attempt escape. The situation escalates when Andi returns, ultimately locking her in even tighter, and revealing his true nature when he subdues her after she's erupted in a desperate rage.
In the days that follow, Clare discovers that she is not the only female within these walls, realizing previous occupants met horrific fates. Andi’s duality becomes increasingly evident as he oscillates between seemingly tender gestures and forcing Clare into submission, further heated by his jealous and controlling demeanor. With her desperation growing, Clare begins plotting her escape, yet she remains under constant surveillance and intimidation.
On Christmas, the atmosphere shifts. Clare attempts to adapt—bonding with Andi and even engaging in moments of affection. The dynamics shift dramatically when Clare discovers Andi's dark past and violent tendencies after witnessing his cruel interactions with a friendly student. She finds solace in minor victories, yet the constant threat of Andi's unpredictable behavior looms large.
As the tension mounts, Clare makes a final desperate attempt to gain her freedom. She takes the opportunity to strike back when Andi is vulnerable, leading to a fierce struggle for control over her fate. In the climactic final act, Clare manages to turn the tables, foiling Andi's manipulative grasp just as he notices she's missing.
Ultimately, her burst of determination leads Clare to freedom, the promise of renewal ringing in her ears as she tosses the keys back at Andi, delighting in her newfound liberation. With a final glimpse of Andi left behind, the film culminates in Clare's victorious escape, symbolizing resilience and the relentless pursuit of autonomy amidst bleak circumstances.
