The comic Jim Gaffigan takes a deep dive into the dark side with “American Dreamer,” an almost relentlessly downbeat character study in despair. It’s a thriller with no hero, just a funnyman who tosses aside his amusing baggage even when he desperately needs it just to keep our sympathy from start to finish.

Things weren’t always this bleak for Cam. He had a wife and son, had a job in tech, had a nice new Impala.

Now he’s piling up the miles on that Chevy for Hail — Lyft or Uber by another name — in Norfolk, Virginia.

He can paste on a smile and try to make small talk. That doesn’t keep the cheap locals from stiffing him out of his tip.

The wife (Tammy Blanchard)? He can’t just show up, hoping to see his son, to give him a toy car he picked up on impulse at a discount store. She calls the cops on him the moment he rolls into the driveway.

“Sir, I need you to calm down.”

The good job and marriage are long gone. He’s behind on child support, slack-jawed, deflated and defeated.

“I’m doing great!” doesn’t have the ring of truth when he’s calling a sibling to beg for cash, putting on a brave face for a former colleague about his job loss, “that whole thing that happened.”

His wife and brother provide the final clues — “Are you taking your medication?” “You need to be in some kind of facility.”

Thank goodness he has a side hustle, driving “off duty” for this guy who likes nothing better than an unassuming, late model Chevy where he can stash the bag in the trunk, driven around by a pasty-faced redheaded 50 year-old.

Mazz (Robbie Jones, fierce and cruel) is a drug dealer, not shy about trotting out the menace or whipping out a pistol, a man who wears his street cred on his game face. Cam is just another minion to him, a $200 a day driver.

“Turn that frown upside down, n—a! You alright!”

He brutalizes underlings. Cam he just bullies. Maybe that’s why the guy at his wit’s end, who shows flashes of compassion and hints of an unmedicated temper, decides on a half-assed kidnapping scheme to score some quick cash.

I only have to use the word “toddler” to touch on the dread that hangs over “American Dreamer” the moment this crime against a criminal enterprise begins.

We can only hope that the compassionate and caring Cam let us see earlier will save one and all. But as the mayhem he unleashes unfolds, a frantic trigger-happy hunt through port town Norfolk’s underworld, it’s just Jim Gaffigan’s affable on-stage persona that we cling to. We hope against hope that things will work out, that we can root for this on-the-spectrum wreck whose actions wreak havoc.

But Gaffigan is so far removed from that pre-“Dreamer” persona that he makes this leap an impossible one. His reactions to the horrors he overhears and sees, which he has to know he’s caused, have a touch of shock about them.

Cam seems numb or dumb to it all — the pistol whippings, threats and executions. His lack of empathy is contagious. Why, exactly, are we pulling for him?

Co-writer/director Derrick Borte (“The Joneses”) gets a spot-on turn from Robbie Jones (“Hurricane Season,” TV’s “The Fix”) and from Isabel Arraiza as Mazz’s baby mama. And he gives Gaffigan some great scenes showing how low he’s fallen.

“You look like s–t!”

“No I don’t!”

But his star doesn’t give us anything to cling to when the s–t hits the fan. As with Borte’s other films (“London Town”), there’s a disquieting lack of connection, a remove from the humanity of it all that may be by design, but weighs on the film and makes our experience of it a lot like Cam’s experience of life — deflating.

Why exactly do we root for him? Because he’s a disaffected white guy on a downward spiral, so whatever carnage he causes in this Afro-Latino world he dabbles in doesn’t matter?

Gaffigan is getting a lot of credit for trying something this grim, and while it’s deserved, it seems a bit beyond his reach. Something closer to Will Farrell’s “Everything Must Go” performance would have helped here — a lighter touch, flashes of humanity, pathos.

“American Dreamer” is riveting to sit through, but too pitiless to embrace.

MPAA Rating:R for disturbing material, violence, some strong sexual content, pervasive language, and drug use

Cast: Jim Gaffigan, Robbie Jones, Isabel Arraiza, Tammy Blanchard, Alejandro Hernandez

Credits: Directed by Derrick Borte, script by Derrick Borte, Daniel Forte A Saban Films release.

Running time: 1:38