In the remote Icelandic countryside, a childless couple, María and Ingvar, live a solitary existence, raising sheep on their farm. The couple's daily routine revolves around their livestock and the rugged, expansive landscape that surrounds them. Their world is turned upside down when they make a shocking discovery during lambing season: one of the newborn lambs carries an unexpected secret that defies the boundaries of nature. María and Ingvar decide to take the lamb into their home as their own, fostering a sense of rejuvenation and happiness that they haven't felt in years. The couple treats the lamb as their child, naming her Ada and providing her with love and care.

As the seasons change, the family settles into a newfound harmony, revelling in the joy their unusual "daughter" brings them. However, their unorthodox decision does not go unnoticed by nature or the local community. Ingvar's brother, Pétur, arrives unexpectedly, bringing with him questions about the couple's moral judgment and the consequences of their actions. The presence of Ada also begins to attract unsettling occurrences, hinting at the delicate balance they have disturbed. The couple struggles with the mounting pressures from the outside world and the increasingly evident complexities stemming from their choice, as they attempt to maintain the peaceful life they've built with Ada.