“Who hasn’t at least thought about it?” Howard Wakefield narrates, pleading his case.

The idea of just…checking out, fleeing the scene, disappearing — Howard makes it feel like a logical alternative to participating in and walking through “the slow trajectory of a collapsing civilization.”

But Howard (Bryan Cranston) isn’t content to flee a testy, turbulent marriage. No. He’ll drop out of sight, simply not show up at work or at home. More self-absorbed than self-aware, he’ll park his Mercedes in the suburban New York home’s detached garage. He’ll close the garage door.

He’ll hie it to the rarely-used attic of the garage, and like Tom Sawyer and Huck Finn, see what happens with those he left behind.

That’s the simple, revealing and darkly comic premise of “Wakefield,” a film by writer (“The Curious Case of Benjamin Button”) turned writer-director Robin Swicord, a movie meditation on marriage, family and surviving both by taking the time to examine what’s wrong.

“What is so sacrosanct about a marriage and a family that you should have to live in it — every single day?”

Howard’s wife, the one-time ballet dancer Diana (Jennifer Garner, regaining her edge), makes him jealous — or so he claims — by strutting around in her dancer-bod-nudity in front of open windows, by paying too much attention to other men who cross their paths at parties and the like.

“All I want is to get through the day,” she sighs, in a flashback. “That’s all I think about. ‘Just get through the day.'”

Married 15 years, they have two daughters entering their teens. They, too, tolerate Howard. Do any of them love him? Will they miss him in the least?

Slipping off to hide in that attic is one impulsive way to find out.

There are just a couple of flashbacks with dialogue exposing the nature of the marriage and the guilt-ridden courtship in which Howard stole Diana from his best friend (Jason O’Mara of “Agents of S.H.I.E.L.D.”).

The rest of the film is Howard’s odyssey, his lengthy (too lengthy) interior and exterior monologues — mimicking the voices of others, losing himself in his own head and scavenging like the raccoon who “inspires” his exile, “surviving…literally, on garbage” like a “castaway.”

Or a homeless bum, like the ones he competes with for left-overs.

Swicord wrings every last dramatic possibility out of this thin premise, and then some. It’s still an 84 minute movie straining to escape a 108 minute one.

Cranston treats Howard like the tour de force he is, man-of-means, solitary philosopher and man-of-action scrambling to avoid detection, asserting himself on “the streets,” losing his humanity but not himself as he descends into bearded madness.

The one deft bit of directorial cleverness (dictated by her script) has Swicord playing out Diana’s saga — from the first moments of annoyance that Howard isn’t on time, to the inept police visit to the grief, and then flinty way she resolves to let life go on — in pantomime. Garner defty navigates this emotional journey without us hearing a word she says — to colleagues and others who might want to comfort her, to her mother (Beverly D’Angelo), to her dealings with her seemingly un-impacted twin daughters.

Garner makes us see what Howard must see for himself. Girlfriend will be fine without you around, the “trap” of a disappearance (not death or divorce, with monetary settlements) notwithstanding.

“Wakefield” is a sometimes funny, always smart movie that never quite finds the depth to be brilliant. But Cranston and Garner give it life beyond the narrow concept and make us care about this selfish man and bitter woman, something few screen romances — even the ones where the characters share scores of scenes together — can manage these days.

MPAA Rating: R for some sexual material and language

Cast: Bryan Cranston, Jennifer Garner

Credits: Written and directed by Robin Swicord. An IFC release.

Running time: 1:48