Lance Henriksen stars as Viggo Mortensen's difficult father in the latter's directing debut.

Having quietly spent years augmenting his acting work with prodigious output in music, poetry and visual arts (not to mention founding a publishing house that champions other artists' work), Viggo Mortensen finally takes the director's chair in Falling, a masterful family drama taking a compassionate view of a father whose faults are impossible to ignore. Playing the son who must now care for him through bouts of dementia while absorbing his insults, Mortensen co-stars with Lance Henriksen, a beloved character actor who has almost certainly never had such a meaty part — with 250 roles on his IMDb page, one can't claim to have watched them all — and who undeniably rises to the occasion. Sundance attendees shouldn't read anything into programmers' placement of this artful film at the tail end of the schedule: This will be one of the fest's most assured directing debuts, and is sure to move viewers whether or not their own families contain a figure as problematic as Henriksen's Willis Peterson.

We see Willis first as a young man — played by Sverrir Gudnason (Borg vs. McEnroe), who both looks like he could've been Mortensen's father and, as the film weaves through its then-and-now storytelling, captures how genuine paternal pride and love for his wife are poisoned by fundamental emotional flaws. Bringing his wife Gwen (Hannah Gross) and newborn son home from the hospital, he stands in the kitchen, holds the baby still while Gwen fetches a clean diaper, and bends over to gently say, "I'm sorry I brought you into this world. To die."

Moving to the present, Willis has acknowledged (in an increasingly rare clear-headed moment) that he can no longer maintain the upstate New York farm where he lives alone, having chased two wives away. He's flying to California with his grown son John (we'll meet John's sister, played by Laura Linney, later), and is having a confused episode. Willis believes the plane is his old farmhouse; thinks Gwen is upstairs; and disturbs both passengers and crew. John does his best to calm him, and the film flashes back to one of the moments that cemented his sense of filial duty: Willis, out by a lake with the 4-year-old John (Grady McKenzie), patiently helping him shoot his first duck, then cheerfully allowing him to treat the dead bird like a pet until it's time to cook and eat it.

Mortensen (who also wrote the screenplay) moves back and forth like this throughout — both to gently illustrate Willis' failings as a husband and father, and to suggest how the old man is experiencing the world today. His confusion about facts is easy to understand, but Mortensen and editor Ronald Sanders use frequent glimpses of the outdoors to add dimension to the character's emotional life. There's nothing Malicky about Willis' connection to nature here, but his obvious affinity for its pleasures makes his inability to connect with humans who love him more poignant.

Willis is a homophobe whose son is gay. As he settles into the home John shares with his husband, Eric (Terry Chen), and daughter Monica (Gabby Velis), he relishes needling the two men, allowing himself to forget, say, that Eric's ancestry isn't Japanese. He speaks freely and loudly about sexuality, genially throwing slurs around in a museum or restaurant. He's also given to casually calling his ex-wives "whores." He sees betrayal everywhere; his fantasies of being cuckolded may have been self-fulfilling prophesies, and play out for him in an eternal present tense: Both women have died, but he rants as if they're quietly in the next room, cavorting with the mailman.

Despite his disregard for others' feelings, Willis is able to connect warmly with the couple's daughter, who overlooks his inappropriateness and calls him her friend. All these contradictions and more fit seamlessly into Henriksen's agile, engaging performance; few moviegoers who've enjoyed him over the years will be surprised, but many will resent that we, and he, have waited so long for a role like this.

Mortensen, who reportedly only agreed to act in his film to secure financing, makes John uncommon among the many adults we've watched cope with difficult parents in indie films. He's not self-righteous or comically exasperated, doesn't quietly complain to Eric about his plight, doesn't rise to the bait his father dangles in front of him. He has fought with him in the past, and grown. Now, he lets insults sail by and patiently adjusts plans to suit Willis' capriciousness. Clearly, this is because John is more decent than those of us who might cut our losses with a similar family member. But perhaps it's also because the past is as alive for him as for Willis: Maybe John is still the mop-headed kid who soaked up his father's approval when he aimed that rifle and shot, and whose father said there was no harm in letting him bathe that beautiful dead duck, dry it by the fire and keep it beside him in bed. Falling doesn't transform its emotional landscape into a simple question of rejection or forgiveness. It's comfortable knowing that meanness and affection can exist in the same person, and that tolerance, even when it only flows in one direction, benefits both giver and recipient.