The most terrifying moment we ever experience is the realization that we are responsible for the life of the perfect being who has turned us from people into parents. We want more than anything to keep them safe and teach them everything they need to survive, even though we know how impossible it is to do both at once. “The Road,” based on the acclaimed novel by Cormac McCarthy (No Country for Old Men) takes that conflict to the extreme with an archetypal father and son (just known as “Man” and “Boy”) and on a post-apocalyptic journey.

We do not know what the cataclysmic event was. We do not know if it was a natural disaster or the result of some kind of attack. But the world as we know it has ended. Sometimes the Man (Viggo Mortensen) goes back to the before in his dreams, of the night before his son was born, the last night when life still held possibilities. Since that day, everything is wiped out, including plants and animals. It is always cold. There is nothing to eat. Almost everyone has died or committed suicide. Those that are left are either predators or prey.

Stripped down to essentials, the Man has just one occupation — protecting the Boy, physically and psychically. As all parents must, he tries to help his son make sense of the world around him, teaching him enough about treachery and danger to be safe but teaching him enough about hope and honor to be “the good guys.” The Man tells his son that he must always carry the fire and by that he means both the literal fire that keeps them alive in the eternal winter and the spirit of optimism and humanity that is as important to the fate of the world as their ability to find something to eat.

As they go toward the coast, for no other reason than that it might be better than where they are and because it gives them a goal, they have encounters that are sad, strange, and scary. They find a somehow-overlooked relic of the past, a can of Coke, as exotic and inexplicable for the Boy as a shard of Sumerian pottery might be to us. When they find the house the Man grew up in, the markings his parents made to measure his growth are still there, a symbol of stability and care. When he tells the Boy that this is the fireplace mantel where they used to hang their stockings, he realizes that memory has any no connection to the Boy’s entire lifetime of scrounging, moving, and staying away from desperate packs of people who might as well be zombies for all of the humanity they have retained.

Wrenching, elegiac, but ultimately inspiring, this is a film that knows how to hold onto its own fire. By stripping away everything but the essentials, it makes us ask ourselves about the compromises we make, the consequences of our choices, and the value of the things that we so often think are worth striving for.