Marina Abramovic, watch your back! The beloved avatar of contemporary performance-based art is one of the targets (and apparent inspirations) for Miriam, the prickly art-world star at the center of Jordan Seavey’s new play, The Seven Year Disappear. Cynthia Nixon brings a hilarious hauteur to the role, a sharp-elbowed solipsism that allows for praise of her real-world rival (“I love Marina, she’s a friend“) as well as bitterness when a major museum announces a new commission or exhibit (“she’s such a fucking hypocrite”).

Unfortunately, Seavey shifts much of the focus of his art-world satire — which opened Monday in a New Group production at the Pershing Square Signature Center — to Miriam’s deeply troubled 30ish son, Naphtali, played with polished panache by Taylor Trensch. Naphtali is a Metropolitan Museum of Art-sized mess, the walking argument for why some self-centered creative types should not try to have children of their own. In addition to the burden of his name — the Hebrew word for “my struggle, my strife,” he explains to a Gen Z nail salon worker — Naphtali is also a recovering alcoholic who soon turns to meth. He’s a gay man who continually chooses the wrong partner (including an older, married gallery owner named Wolfgang who had been involved with his mom and served as a kind of stepfather figure). And he’s a young adult who’s entirely dependent on his mother for employment, serving as her manager for major bookings and commissions, which have mostly dried up as the show begins.

They have a codependency that’s alarmingly lopsided — a fact that is exacerbated by her disappearance just moments before she was to give a speech describing a new commission by the Museum of Modern Art. Is this her new work? Even Wolfgang assumes that Naphtali is in the loop on Miriam’s plans, but he becomes unmoored by the loss of both his mother and employer. He turns to drugs and political work, which both lead to catastrophic disappointment (he worked on Hillary Clinton’s presidential campaign).

Trensch carries his wide-eyed boyishness in a backwards-jumping narrative that starts just after Clinton’s 2016 loss to the disastrous 2009 announcement at MoMA. Nixon, meanwhile, sinks into seven additional roles, from the German-accented Wolfgang to a backward-cap-wearing Bernie Sanders backer to a well-meaning but easily distracted Hollywood starlet. She brings a striking individuality to each role with a minimum of outward stylistic cues. (Both actors are dressed in identical black coveralls, designed by Qween Jean.) Director Scott Elliott also makes good use of Derek McLane’s screen-dominated set design and projections (by John Narun) that mimic video-based gallery pieces while also allowing us to see scenes taking place offstage.

Seavey’s script is at its sharpest when the focus remains on Miriam — a uniquely self-made monster. A Peoria-born convert to Judaism, she’s the sort of solipsist who nonetheless invokes a personal legacy that includes centuries of slavery, exile and genocide. “Don’t you dare discount my Jewishness on a technicality,” she tells Naphtali when he gently chides her about her goyish upbringing. None of Naphtali’s other encounters come close to matching the spark of those mother-son exchanges, which culminate in Miriam’s unexpected return and her absurd assumption that her relationship with Naphtali can resume exactly as before. (One quibble: These exchanges can veer into the shouty; the emotions, while genuine, would be more powerful if allowed to simmer just below, or even at, the boiling point.)

The Seven Year Disappear is a juicy showcase for Nixon, who emerges as an unexpected shape-shifter among characters that are far removed from the ones for which she has become best known in the public eye.