It’s difficult to think of a play more quintessentially Irish than Conor McPherson’s 2007 drama, The Seafarer, now playing at the Santa Paula Theater Center. By turns profane, tender, vicious and funny, it never long escapes the undercurrent of darkness that pulls like a riptide at even its lightest moments.

The play unfolds on a single day, in a single room: Christmas Eve at the Dublin home of brothers Richard (Michael Perlmutter) and Sharky (Taylor Kasch), two lost souls making their way in the world by making do. Richard, recently blinded and perpetually three sheets to the wind, bellows orders from his armchair and raps his glass for refills.

Sharky cares for his brother, tries not to drink and not to think about his boss’s wife, or his ex, Eileen, now living with their friend Nicky (Scott Blanchard).

But when Nicky shows up with Mr. Lockhart (David Newcomer), a dapper stranger bent on playing cards with his new friends, so begins a marathon, whiskey-soaked night with far more at stake than a few euros. Mr. Lockhart knows Sharky’s past, and there is no way he’ll let him forget it — no way in hell.

For hell, it turns out, is Mr. Lockhart’s home country. Perhaps it’s no accident he takes a name evoking frigidity and isolation, for as he solemnly tells Sharky, “I am the very power that keeps [people] apart.” Sharky bet against the devil years ago, and now the devil has returned to exact his payment, unless Sharky can turn the tables.

Michael Carnahan’s artfully haphazard set design captures a family teetering on the brink of dysfunction: Magazines slide off sloppy piles, overturned bottles of whiskey litter the floor, threadbare rugs lie askew. Justine Abbitt’s understated costumes likewise communicate with economy even offstage characters’ personalities: we learn far more about Eileen’s taste in men from Nicky’s leather jacket than any cell phone exchange.

The play’s pacing over the nearly three-hour stretch works beautifully, alternating between chaotic card scenes and quiet moments of terror when Lockhart describes what awaits Sharky should he lose. Sharky may grind with self-loathing here, but in hell, Lockhart assures him, it’s much worse. “There’s no one to love you.”

Nothing in McPherson’s rendering of Mr. Lockhart will surprise audience members familiar with Faustian tales. His Mephistopheles as played by Newcomer is intelligent, refined, wily, but ultimately fair. And the plot’s faint predictability makes it no less effective. The story ultimately hinges not on Sharky’s relationship with the supernatural character, but the human ones.

Perlmutter gives a tour-de-force performance as a bullish tyrant hauling himself around on an upended cane, crook to the floor. His flare-ups blaze bright, but burn cool. We even see occasional moments of fondness, as when he reassures the hapless Ivan (a charming Eric J. Stein) about his marital troubles. It’s Kasch’s Sharky we worry about, brooding and withdrawn, who smolders as steadily and hot as a peat fire.

Throughout the play we witness the seesaw between Richard and Sharky, as first one then the other gives in to childish explosions. What becomes clear, despite their squabbles, is that these brothers love each other, and they know how to rescue each other.  

McPherson’s thesis, if you want to call it that, posits that this sorry, broken mess we slog through still outshines any alternative. If that sounds a bit too pat, it doesn’t overshadow this powerful play. What redemption exists must be found in human affection, guiding us like a candle in the window on a dark winter night. 

The Seafarer, through Oct. 16, Santa Paula Theater Center, 125 S. Seventh Street, Santa Paula. For reservations, 805-525-4645.