The headless black-comedy "Heartless" is not Sam Shepard's best play. It is not his ninth-best play. You could call it a return to form, and its hell-for-leather riffing does resemble Shepard’s early work, his grand junk-collage "Tooth of Crime" jazz-odysseys. But you could also say, less charitably, that "Heartless" feels like a young man's play reworked, overworked, and worked-over by a now-much-older man. From its thudding title on down, the show feels like the pomo playwright’s version of a curmudgeonly “dad-joke”: I detected, beneath the Shepard-y obscurantism, a lot of metaphysical head-shaking and beard-stroking and general incomprehension when it comes to subjects like Women and Youth and the New Exhibitionism. What's up with all the Twattling and Facetubing, anyway?

Actually, that’s giving "Heartless" way too much credit for currency: As we ramble through a weekend in the Hell-A Hills with Sally, a bitter youngish Angeleno dilettante (Julianne Nicholson) who bears a mysterious dollar-matinee chest scar, the most modern device on display is her chunky video camera, which she uses to film her new old-boyfriend, sixtysomething lost-soul Roscoe (Gary Cole, taking big swings at a role that isn’t really there). Roscoe doesn’t understand her desire to document everything, feels threatened by it. We mostly feel baffled by it, because Sally’s exhibitionism-voyeurism doesn’t really resonate with anything in the play or much in the culture-at-large (beyond the obligatory harrumphs about “reality television,” a phrase that officially sounds ancient and cries out for a blanket ban).

Not much about Sally resonates, actually. We know she’s missing a piece of herself—we even know which piece—and that she’s living on borrowed, possibly stolen time. But this un-buried child is a very-writerly chaos, and not a particularly interesting one. As interpreted by Nicholson, Sally is simply sullen, spiteful, a drag. She’s supposed to be the profound absence around which the rest of the play rotates, but there’s no attraction, just repulsion - and, more often than not, indifference.

So why, with all these debits, did I count this an enjoyable night at the theater? Because when there’s real talent and maybe a touch of terror onstage—every actor looks vaguely scared, as if she herself doesn’t quite know what’s going to happen next—my attention never wanders. Director Daniel Aukin (4000 Miles) has no idea what to do with the trunkful of body-parts Shepard has parked in his driveway, so he gives his fantastically hambone ensemble free reign. If you thought the RNC was an endless parade of sociopaths, mountebanks, and paranoiac mutterers, wait until you get a load of this Convention of Crazies. Lois Smith arrives onstage in a wheelchair and instantly begins channeling the spirits of every mad matriarch from the American stage canon. Her older daughter Lucy (In the Wake’s Jenny Bacon) plays dolorous counterpoint to Smith’s brays and glissandos; she’s in another play entirely, but she stakes out her moments in the spoitlight. And Betty Gilpin, in a near-silent performance as Mable's enigmatic nursemaid, proves herself a transfixing bit of dirty Hitchcock graffiti. "Heartless", when it's wordless, almost says something. Almost. But don’t listen too hard, or the whole thing starts to decompensate. Just sit back and drown in the sound.