A man and his child trek towards the southern sea in hopes of finding a hospitable environment for survival. The planet has been devastated by a catastrophic event that occurred shortly before the child was born, which resulted in the annihilation of human civilization and the planet's life-sustaining ecosystems. As a result, the child has never witnessed natural life or celestial bodies, and both he and his father must wear masks to shield themselves from the omnipresent ash particles that linger in the air from the disaster.

The duo shares a profound love and sense of duty to each other, as survival depends on their relentless journey down the road as they scavenge for necessary resources from the remnants of the world that once was. Along their journey through the bleak and frigid landscape, they encounter the full range of human behaviors, some heartening and others deeply disturbing. They strive to keep alive the memories and values of a time long gone, in a world where the past and future have been wiped out in a singular cataclysmic event.

Their story begins with them navigating through mountainous terrain, their possessions carried in a shopping cart which includes basics such as food, survival tools, and a few toys for distraction. As they attempt to eke out a living from the left overs of civilization, other survivors have descended into utter savagery, resorting to cannibalism in a world devoid of agriculture, animals, and modern technology. The pair constantly remain on guard against such vicious marauders, with the father keeping the final two bullets in his gun for their own use if necessary. Despite the constant fear and hunger, they stumble upon caches of provisions left behind by those who once hoped for a future, offering temporary respite. The son's quick maturity comes with a strong conscience, and his empathetic and compassionate nature remains untouched despite the harsh realities of their world.

Ultimately, they reach the coast but the relentless journey has taken a toll on the father's health. He breaks his promise to his son by dying, leaving him alone in the world. He reassures his son before dying that he will find goodness even in his absence. After spending three days mourning his father's death, the boy is approached by a stranger, who offers him a place in his family. After a thorough interrogation regarding their ethics, the boy decides to join them, marking a new chapter in his survival journey.