Don’t look for Alice in Wonderland in Rabbit Hole, the profound and heartbreaking new play by David Lindsay-Abaire. The title may hint at Lewis Carroll-and, indeed, a certain Mad Hatter absurdity is what you might expect from this ingenious dramatist, whose previous works featured quirky happenings and far-fetched situations. But Lindsay-Abaire’s first Broadway outing turns out to be a beautifully controlled piece of realism that tells a harrowing story about loss and healing. There may be a looking-glass reality here, but it’s the reality of grief.

Earlier this year, the Manhattan Theater Club production received substantial media attention for its casting coup: the show stars Cynthia Nixon, best known for portraying the lawyer Miranda on HBO’s Sex and the City. In Rabbit Hole, she plays Becca, a suburbanite who’s struggling to recover, along with her yuppie husband Howie (John Slattery), from the accidental death of the couple’s four-year-old son. As she drifts through a house still rife with painful reminders-baby clothes, toys, even the family dog-Becca finds herself alienated from Howie, trapped in her own isolating sorrow. Meanwhile, despite good intentions, Becca’s loud-mouthed mother Nat (Tyne Daly) and ditzy sister Izzy (Mary Catherine Garrison) only make the situation more agonizing.

Lindsay-Abaire’s earlier plays also showcased beleaguered female characters. Fuddy Meers, his zany breakout piece, revolved around a woman who woke each morning with a brand-new case of amnesia. The comedy Kimberly Akimbo centered on a teenager with a rare aging disease, and Wonder of the World sent its heroine fleeing through a grotesque landscape to Niagara Falls. In Rabbit Hole, it’s as if all that madcap energy has been funneled into a streamlined form-a wrenching story that’s seeded with funny lines, and ultimately speaks about human resilience.

Gracefully directed by Daniel Sullivan, Rabbit Hole reminds us how loss can give cozy details a harrowing edge. One of the play’s most wrenching moments occurs when Becca fetches a glass of milk for Jason (John Gallagher Jr.), the local teenager responsible for the tragedy, whose guilt forces him to stop by several months after the accident. As both actors quietly let the moment resound-like all the show’s performers, these two are riveting-the action seems all the more terrible because it is so simple. In other scenes, too, tokens of domesticity (a stuffed Curious George doll, a cup of crème caramel, a basket of laundry) turn into measures of tragedy.

But the play also moves past the material world to touch on metaphysics. “People want things to make sense,” Nat says as she urges her daughter to grasp some kind-any kind-of philosophical comfort. But Becca is convinced that her loss does not, in fact, make sense, and she particularly hates the way the forlorn parents in her support group have turned to religion. Ultimately, she herself finds solace not in religion or philosophy but in a notion from a science-fiction story: the “rabbit hole” of the title refers to the idea that there are innumerable parallel universes, each accessible through a “rabbit hole” entry point, and each presenting a variation on our own world. In some of those alternate universes, Becca reflects, she is happy. The concept seems to offer another kind of faith.

Personal misfortune has more sensational consequences in the plot of another high-profile production: the acclaimed revival of Sweeney Todd: The Demon Barber of Fleet Street. Director John Doyle generated buzz for his United Kingdom version of this Stephen Sondheim musical, cast with actor-singers who doubled as instrumentalists. Now he has repeated the feat in New York, where the show stars two big Broadway names and former Tony winners, Michael Cerveris and Patti LuPone.

Prospective audiences should, though, be duly warned: Sweeney Todd is an intense and disturbing experience, a play that might prey on your nerves if you are alone in the house afterward. With its eerie, operatic textures and occasional dissonance, Sondheim’s music underscores the morbidity of the story, which is pretty unsettling to begin with. With a book by Hugh Wheeler (adapted from a play by Christopher Bond, in turn derived from an 1847 melodrama), the musical relates how a barber, Sweeney Todd, returns to London to take revenge on those responsible for imprisoning him. The tale takes a gruesome twist when Sweeney’s pal Mrs. Lovett hits on the idea of using human bodies as filling for the meat pies she sells.

Director Doyle ratchets up the emotional voltage by keeping the ten dynamic performers on stage the entire time, shuttling back and forth between the musical instruments and the downstage space where a wooden coffin is prominently located. LuPone provides a touch of grim comedy now and then with her impish tuba playing and her sassy depiction of Mrs. Lovett. Otherwise, the aesthetic is grim: performers wear black and white, creating a stark palette that’s relieved only by the odd stream of blood, ladled out of big pails. Otherwise, the only relief for the eye is a towering shelf of objects: books, pans, a bird cage, sculptural heads, a model of a hand.

The antirealistic look adds to the production’s shocking bleakness: since there’s no depiction of Victorian London, you can’t console yourself with the feeling that happiness may be taking place just around the corner. No reassuring parallel universes here: just Sweeney’s grim reality-resentment, crime, and vengeance. You don’t have to be too theologically minded to see it as a world from which charity and forgiveness have been drained: Sondheim’s lyrics do, after all, instruct us to “attend the tale of Sweeney Todd / He served a dark and vengeful god.”