In the 1960s, set in a mysterious part of the Alps, a pair of eagles faces a difficult choice as they welcome two eaglets into the world. Their mother, knowing the harsh realities of nature, decides she can only raise one to be her successor. Tragedy strikes as a rival eagle causes the eaglets' father to plummet to his demise. Following this, one eager fledgling falls from the nest, but, adhering to her instinct, their mother disregards the fallen eaglet's desperate cries for help, focusing solely on the survivor.
In a nearby forest, forester Danzer (Jean Reno) encounters young Lukas (Manuel Camacho) and his father Keller (Tobias Moretti). The duo is settling into a new life in the mountains after the tragic loss of Maria (Eva Kuen), Lukas's mother and Keller's wife, who perished in a fire. Devastated by Maria's death, Keller struggles to connect with Lukas, who finds solace in nature, gradually retreating from his father's presence. In moments of reflection, Lukas often returns to the remnants of their old home, where he cherishes the memories captured in a photograph of his mother.
During an outing, while accompanied by his loyal dog Scout, Lukas discovers the injured eaglet and makes the heartfelt decision to nurture it back to health. He brings the eaglet to the ruins of his old home where he can provide the care it desperately needs. Danzer soon learns of the eaglet's plight and chooses to assist Lukas out of compassion for the young boy.
With insightful guidance, Danzer informs Lukas about the importance of proper nutrition and ample sunlight for the eaglet's recovery. Tensions escalate when a cunning fox attacks Keller's chickens, leading him to further lash out at Lukas in frustration. Concerned for the eaglet’s safety, Lukas takes refuge in his family’s hut. He bravely protects the eaglet from the foxes' threat. While reading the family Bible, Lukas stumbles upon the biblical tale of Cain and Abel, which resonates deeply with his own situation, prompting him to name the eaglet Abel.
As Lukas continues to nurture Abel, Danzer visits and invites Lukas to spend the summer at his home in the mountains, allowing Abel to accompany them. With newfound hope, Lukas catches a fish to feed Abel, although the eaglet escapes its grasp. Unbeknownst to them, Abel's mother remains vigilant, hunting for her young.
As both Abel and his sibling grow stronger, Lukas becomes determined to help Abel take flight. With each passing day, Abel's wings flourish, and he begins to soar gracefully through the air. However, one day Abel disappears, leaving Lukas heartbroken. In his yearning, he observes Abel flying freely, yet as he tries to reach out, the eaglet flutters away, deepening Lukas's sorrow. Danzer attempts to console him, explaining that Abel yearns for the wilderness, while admitting his uncertainty about Abel's fate.
Abel faces challenges as he tries to hunt, struggling to find food. Lukas remains preoccupied with the knowledge of two ominous threats—Keller's shotgun and Abel's rival brother, whom he has aptly named Cain. After several days apart, Abel finally returns, prompting Danzer to offer Lukas guidance on training the eaglet to hunt. However, they clash with Keller over Danzer's unconventional methods. Despite their differences, they push forward with their training plan.
A moment of panic ensues when Lukas and Danzer suspect that Abel might target Scout, but they soon realize Abel has successfully caught a weasel instead. Danzer tells Lukas that while it’s painful to accept, the day will come when Abel must learn to leave. With a heavy heart, Lukas agrees as they prepare to take Abel to an unfamiliar area of the mountains for his freedom.
As winter sets in, Abel becomes adept at finding and sustaining himself. Lukas, filled with nostalgia, constructs a small memorial with stones and one of Abel's feathers. Awakened from slumber one night, Lukas encounters a threatening wolf. In the chaos, he accidentally triggers a bear trap. Luckily, Danzer, nearby, wards off the wolf and treats Lukas's injuries. Yet, the divide between Lukas and Keller deepens, casting a shadow over their relationship.
Danzer shares the tale of the Brothers of the Wind with Lukas, who wonders about the fate of the characters beyond the written story. Finally, Lukas decides he can no longer stay with Keller. Their confrontation escalates when Keller asks Lukas to light a match, igniting a moment that leads Lukas to believe his father may have played a role in his mother’s death. As he flees into the mountains in search of Abel, he is trapped by a rockslide caused by a fleeing fox, leaving him unconscious after a lightning bolt strikes nearby. Abel circles above, witnessing this, while Keller rescues Lukas, offering an apology for his earlier behavior. Tragically, another eagle falls victim to the stone cascade.
In a twist of fate, two years later, Lukas and Keller find themselves wandering together again. Lukas expresses a sense of connection, believing that Abel is still with them, but Keller informs him that the dead eagle they found belonged to Abel. Keller urges Lukas to extend his arm, and miraculously, Abel appears, settling on Lukas' arm. Today, with a bittersweet resolve, Lukas removes the bracelet he made for Abel long ago, letting the eagle soar into the vast sky above. As Danzer looks on from a distance, Abel flies higher, accompanied by a female eagle, signifying the continuation of their legacy and the eternal cycle of life.
