The events of the film unfold in 1978 within a fictitious town named Acqua Traverse, located in Southern Italy. This period is marked by the oppressive heat of the hottest summer on record and the notorious Years of Lead. At the center of the story is a nine-year-old boy named Michele Amitrano who, along with his close-knit group of friends, embarks on an adventurous race across parched wheat fields towards an isolated farmhouse.
While racing, Michele's sister accompanies them but unfortunately trips and breaks her glasses. Upon hearing her cries, Michele rushes back to comfort her, easing her fears about the glasses. Together, they finally arrive at the farmhouse, albeit as the last to do so, incurring a forfeit in the process. However, rather than punishing them, the group leader, Skull, selects the only other girl in the group, aside from Michele's sister, to face the consequence. Skull orders her to undress, but as she looks to her peers for support, they all turn away. In a brave act, Michele claims the last arrival was him and insists he should take the punishment instead.
Michele's forfeit involves walking across a precarious beam in the old barn at the farmhouse. Afterward, as Michele and his sister make their way home, she inquires about her glasses, prompting Michele to head back and look for them. In his search, he stumbles upon a sheet of metal covering a hole in the ground. Curiosity gets the better of him as he uncovers a part of a bare human leg, sending shockwaves of horror through him. Fearing the consequences if his friends found out, Michele resolves to keep this disturbing discovery a secret, feeling threatened by Skull who might steal his finding.
The following day, Michele returns to the spot, mischievously throwing stones into the hole. While distracted, he suddenly encounters a zombie-like boy emerging from the darkness, causing him to flee in fright. Later, as Michele struggles with a broken bicycle chain on his way home, he receives a scolding for his tardiness. The next day, while playing, Michele can't shake the image of the boy from his mind and decides he must visit him again. He discovers the boy is indeed alive but in a frail state, and Michele begins to supply him with water and food.
As the plot thickens, Michele witnesses a televised report regarding a boy named Filippo, who has been kidnapped from Milan, and the resemblance to the boy he found is striking. He overhears discussions among his parents about keeping the boy concealed, leading to a shocking realization: his father is involved in the kidnapping alongside other townsfolk. During a visit to the boy, Michele reveals his knowledge of his true identity and shares the message from Filippo's mother, though this news does little to comfort the boy who still believes he’s dead.
The friendship deepens as Michele continues to visit Filippo (played by Mattia di Pierro), offering him moments of freedom in the wheat fields despite the risks. In an effort to win a toy for Filippo, Michele shares the secret of his existence with his best friend, Salvatore, who reluctantly partakes in the transaction. Tension escalates when one of the kidnappers, Skull's older brother, catches Michele during a visit and subjects him to violence, while Salvatore betrays him by revealing the secret.
Michele's parents react differently upon discovering his return from the encounter; his mother defends him fiercely, while his father threatens violence if Michele dares to visit Filippo again. Promising to heed his father's warning, Michele wrestles with his conscience until Skull insists the group revisits the farmhouse, only to find the hole empty and Filippo missing. In a twist of fate, Salvatore offers the location of Filippo in exchange for forgiveness.
In a race against time, Michele learns from overheard conversations that Filippo's life hangs in the balance. He rushes to the cave where Filippo is held captive and helps him escape. However, Michele's father arrives, unknowingly posing a lethal threat to his own son when he pulls the trigger, injuring Michele in the leg during a scramble to protect Filippo.
The climactic conclusion sees Michele being carried away by his father, desperately seeking medical help. Just as the looming threat resurfaces, helicopters arrive to apprehend the kidnappers, and in a moment of redemption, Filippo reveals himself to be alive, grateful to Michele. The film closes on an emotional note, emphasizing the bond that has formed between the two boys amid a backdrop of fear and betrayal.
