Sarah, a divorced fertility doctor, is gearing up for her daughter Mia's seventh birthday celebration. Their day takes an unexpected turn when they find a rabbit in their yard, which Mia quickly becomes fond of. As the evening unfolds, they are joined by Peter, Mia's father, along with Denise, Peter's new partner, and her young son, Toby. However, amidst the festivities, a playful incident escalates as Toby accidentally hits Mia on the head, prompting an angry response from Sarah. Despite Sarah's initial outburst, Peter intervenes and calms the situation.
Later that night, a significant moment occurs when Sarah attempts to discard the rabbit by throwing it over the garden wall, only to be bitten for her troubles. This act does not go unnoticed by Mia, leading to increasingly concerning behavior from her daughter. The next day, Mia starts exhibiting strange tendencies, becoming distant and donning a self-made rabbit mask that she refuses to remove. Her school life worsens as she hides in a playground tube, refusing to acknowledge any bullying, while she confesses to missing her estranged grandmother, Joan, whom Mia has never had the chance to meet.
The situation escalates when Mia asks for family pictures to create a family tree. While searching, Sarah comes across a childhood photograph featuring herself and her sister, prompting a shocking revelation when Mia insists she is in the image. As Mia’s demeanor begins to spiral, Sarah's own perception of reality deteriorates, leading to hallucinations and increasingly disturbing dreams, compounded by the infection from the rabbit bite.
In response to Mia's urgent pleas to see Joan, Sarah reluctantly takes her to the assisted living facility where Joan resides. Upon encountering her grandmother, who suffers from dementia, the situation grows tense when Joan mistakenly identifies Mia as "Alice," a name that stirs an intense reaction from the young girl. The ensuing chaos leads Sarah to accidentally injure Mia in the struggle.
As the story unfolds, Sarah discovers unsettling drawings in Mia's schoolwork, unveiling the depth of her daughter’s psychological turmoil. In a tense confrontation, Mia insists that she is Alice—a revelation that infuriates Sarah, especially after recalling painful memories of Alice’s mysterious disappearance at the same age. As hallucinations plague Sarah, her mental state crumbles, culminating in a tragic incident where she accidentally harms Mia with scissors.
Haunted by memories of her sister, Sarah's confusion blurs the lines between Mia and Alice. Disturbing fragments from their shared past resurface, detailing the tragic event when Sarah, in a moment of panic, pushed Alice off a cliff during a childhood scuffle. The stakes rise when Peter arrives home to a chaotic environment, where shattered family photos reveal Sarah’s mental disarray.
As the clock ticks, both Peter and Sarah frantically search for Mia, who has gone missing. The tension peaks when Sarah, racing against time, confronts Joan, finally admitting the heartbreaking truth: Alice is gone. Returning home, she seeks forgiveness from Mia, who bluntly calls her a monster for past actions. The chilling finale unfolds as Sarah looks out the window the next morning, witnessing Mia hand in hand with Alice, moving toward the cliff—a haunting image that encapsulates the fragile nature of their reality.
