The wholly committed John Lithgow and a talented, risk-taking ensemble propel themselves through three hours of family strife and bloody betrayal in the disquieting “King Lear” that has just opened at Central Park’s Delacorte Theater.

John Lee Beatty’s dark set sets the tone for the tragedy, which hasn’t been seen at Shakespeare in the Park since 1973. (Is the three-hour-plus “King Lear” the gentlest summertime fare? Can I ask you again at 11:30 p.m. when you’re waiting for a C train home?) The familiar characters come and go through a half-dozen doors evenly spaced underneath a daunting wall of mesh, with dozens of short spears tucked into it at random intervals. 

It’s a severe and unusual backdrop. Unlike past SITP productions, which have capitalized on The Delacorte’s natural setting, this one—unfolding under the as-swiftly-paced-as-“Lear”-can-be direction of SITP vet Daniel Sullivan (last season’s “The Comedy of Errors,” etc.)—removes any sense that you’re even in Central Park. You might wonder what it would be like if the play’s famous storm on a heath could transpire among trees.

It’s difficult not to have a soft spot for Lithgow’s tragic monarch, here a reasonable fellow blinded, just momentarily, by the insincere flattery of his two oldest daughters, Goneril and Regan (movie star Annette Bening, in her SITP debut, and lauded stage and TV actress Jessica Hecht).

Lithgow uses his lanky body to convey anguish, making his ruler profoundly physical: when Lear is confronted with the reality of his own foolishness, the actor slaps his resonant noggin with a smack that can be heard to the back of the theater (“O Lear, Lear, Lear!”).

Indeed, we are treated to Lithgow on the floor, offering toasted cheese to an invisible mouse when Lear has gone mad—and we see Lithgow’s king lumbering forward at play’s end, bearing the full weight of his dead youngest daughter, Cordelia (the endearing Jessica Collins, of “Zero Dark Thirty”), and wailing like a wounded animal.

It’s magnificent work, aided by virtue of the fact that the two-time Tony winner has been growing a beard for months, to regal effect.

I doubt anyone is heading to the Delacorte expecting to see Bening disappear into the role of deceitful Goneril. The Oscar-nominee, last seen on Broadway in 1988’s “Coastal Disturbances,” is icy and elegant as the disloyal and power-hungry daughter who becomes appalling even to her closest ally, husband Albany (the excellent Christopher Innvar). 

If I have any issue with Bening’s performance, it’s that she may be too sophisticated to fake flattery. When Goneril says: “Sir, I love you more than words can wield the matter; dearer than eye-sight, space and liberty,” you want to believe the character. Bening’s Goneril is already such an … adult, that you have to wonder—how can her dad really fall for this?

As Regan, Hecht (with Bening, below) is batty from the outset, raising her voice in rage and quick to slit a throat. It’s a polarizing performance. Hecht is one of my favorite actresses—she was wonderful earlier this year in “Stage Kiss,” and is recognizable to many as Walter White’s one-time lover on “Breaking Bad”—but the vocal swings here are sometimes distracting.

Days later, I’m still preoccupied by the (surprise!) laugh-inducing performance from Jay O. Sanders, as Lear’s loyal aide Kent, who somehow manages to transcend the misery brought upon everyone else, up to and including the poor Fool (the fine Steven Boyer, behaving like a demonic Harry Potter). 

Kent, after being banished by the king, spends much of “King Lear” in disguise. Props to Sanders, who pulls off the trick with no special costuming, but merely the hint of a Southern Accent. (“True Detective” fans will appreciate the proximity of two of that show’s actors on the same stage—Sanders was the series’s oily Rev. Tuttle, while Cornwall, Regan’s bloated husband, is played by Glenn Fleshler, the swollen “mowing man” of the HBO series.)

A trio of excellent performers tackle the parallel story line, which has the ultimately blinded Gloucester (Clarke Peters, of “The Wire”) at the mercy of sons Edmund (Eric Sheffer Stevens) and Edgar (Chukwudi Iwuji). Stevens and Iwuji are a dynamic pair, the former as yet another ruthless manipulator, the latter a heroic counterpoint. 

A choreographed battle between the two is by far the climax of the production in terms of action, though it may come too late to jar some out of Bard-induced complacency. If you’re worn out by the end of “Lear,” well … you’re supposed to be. There’s only one fellow to take that up with—and it’s not anyone involved with this production.

“King Lear,” through Aug. 17. Tickets are free, and distributed two per person at the Delacorte Theater in Central Park, beginning at 12 p.m. on the day of each performance. More information is available at publictheater.org.

Follow Robert Kahn on Twitter@RobertKahn