It’s not unusual in film to find a parent whose protective instinct is so fierce he will unthinkingly endanger his own life to save his child. But teaching your kid how to blow his own brains out in the event of your own premature demise—that’s a whole different dimension of tough love. Such grim practicalities are strewn throughout The Road, John Hillcoat’s adaptation of the Cormac McCarthy novel that amounts to two hours of bleak with rare, faint glimmers of hope.

Entertaining it is not. “Each day is grayer than the one before,” says the father credited only as Man (Viggo Mortensen), who is traveling with his son (Kodi Smit-McPhee) through the ashen, fiery landscapes of the post-apocalypse, one void of zombies, Terminators, or breathtaking special effects. Viewers don’t find out what kind of catastrophe ended life as we know it in McCarthy’s story (adapted by Joe Penhall), though there are brief, more colorful flashbacks to the pair’s former reality, one replete with laptops, quaint kitchens, and Mom (Charlize Theron). Leaving their home—and, you get the impression, fighting back in the first place—was not a decision on which husband and wife agreed. “They’re going to rape me, and they’re going to rape your son, and then they’re going to kill us and eat us,” she argues through tears in an attempt to keep her family together.

Although “they” is never defined, good versus evil and the bond between father and son are the themes propelling The Road. The former was also the business of 2007’s No Country for Old Men, another McCarthy adaptation, though that film offered a superior storyline and a variety of characters that kept the audience engaged—even enthralled—and earned it a Best Picture win. Here, Mortensen and Australian newcomer Smit-McPhee may deliver intense, often gut-wrenching performances, but their journey is too mysterious and soaked in one-note misery to keep you rapt: When they come across bodies hanging in a barn and the son asks why, the father merely answers, “You know why.” The few people they come across are nearly feral and, except for one old man (Robert Duvall), ready to hurt and rob them—even though money no longer has value. When the boy tells Dad that he had a bad dream, you can’t help but wonder what could be worse than their present reality. (Even in the apocalypse, however, there’s room for product placement: They eventually find a bomb shelter in which Spam and Vitamin Water exist in abundance.)

What is regarded as invaluable in this story—and what a person can’t be robbed of—is a sense of right and wrong, a moral burden often referred to as “the fire.” The man and his son, for example, talk about how they won’t resort to cannibalism, because “we’re the good guys, and we’re carrying the fire.” Faith is apparently important as well, with the Man’s narration boasting that if his son isn’t “the word of God, then God’s never spoken.” Ultimately, The Road is about their relationship, and about the lengths a parent will go to in order to provide. And if the end of this pair’s journey is actually hopeful, you’ll likely feel too battered by the horrors that came before to revel in the moment.