In a remote forest, an abandoned hotel becomes the secluded world for two girls, Alma and Alex, raised by their mother Mother who convinces them that humanity has vanished and that survival means living in isolation. She teaches them about medicinal plants, imposes strict rules, and forbids going outside during the day, claiming the sun could kill them.
At first, life feels harmonious, but as they approach adolescence, the two begin to question their mother’s teachings, their sense of civilization, and their own budding sexuality, especially when Alma experiences her first period. Secretly, they break into a forbidden warehouse and encounter unfamiliar objects—a phone and a pornographic magazine—that expose them to new ideas about the male body and the wider world beyond their borderless refuge.
Days pass, and Alex grows increasingly restless under their mother’s control, while Alma remains more obedient. The mother clings to childhood habits, even writing messages in an attempt to intercept any surviving humans, while Alex longs for independence and connection beyond their secluded life. Tensions mount, and Alma’s nightmares deepen.
One morning, Alma believes Alex has left, but she has not. Alma ventures out during the day, provoking the mother’s anger and fear. In the days that follow, Alex convinces Alma that their mother can no longer be trusted. She urges Alma to send a “message in a bottle” into the black river—the forbidden boundary the mother warns them never to cross. The mother intercepts them and punishes them by locking them in their room. When the door stays sealed for days, the sisters unite, escape, and wander the estate, uncovering the comforts their mother had hidden away. They run away in anger, only to have Alma regret her decision and seek a return home, sparking a fierce argument with Alex, who bolts away.
Frightened, Alma falls and faints. The mother finds her, treats her foot injury, and brings her back. As days slip by, Alma feels increasingly drained, and the mother grows more repressive. Alma begins to suspect something is amiss. When she attempts to swap tea with her mother, the elder woman drifts into a deep sleep, giving Alma the chance to explore outside during the day. This escape proves that the mother’s stories are false. Upon waking, the mother confronts Alma, who decides to leave. A brutal struggle ensues, and Alma flees into the woods. The mother pursues, but she falls into a hole and is fatally pierced. Before dying, the mother guides Alma toward a path of truth: there, Alma discovers Alex, who rescues her from drowning and seems to know what happened.
Together they stumble upon an abandoned car, and Alma is jolted by a memory of a childhood accident: she recalls being kidnapped by a woman who was not her mother. The realization hits hard—she created the alter ego Alex to cope with loneliness. With that revelation, Alma is left alone, facing a society she has never truly known.
