If there is a smaller venue for live theater in the District than Caos on F, I haven’t found it yet. Had I not been there before, only a sandwich board on the sidewalk would have alerted me that—through a door and up an exceptionally noisy flight of stairs—a play was taking place. A left turn down a narrow hallway leads to a small lobby where a desk serves as both box-office and concessions stand. Past the desk is a wall that looks like a whitewashed clapboard exterior of a house with a screen door, through which I enter into the front room of an old home: A small kitchen table with chairs, a sink, and a vintage refrigerator sit to my right; an old sofa is to my left. The books, coffee mugs, and picture frames on the walls make the place look lived in. I am on stage and now understand why late arrivals will not be seated. I look ahead and see just 18 seats; four audience members have arrived before me.

Tiffany Antone‘s Twigs & Bone, receiving its world premiere with Nu Sass, begins with Moira Lane (Aubri O’Connor), dressed in a blue pantsuit and dragging a small suitcase behind her, knocking on the very same door through which I entered moments before. Moira is returning to the home where she was raised. Despite her initial attempt to put on a cheerful exterior, it is fear and wariness that brought her home. The phone has been disconnected for weeks and the eighth housekeeper she hired to keep her parents’ hoarding in check, has been driven away. Her Irish immigrant parents, Bonnie (Lynn Sharp Spears who also directs and serves as prop designer) and William (Tom Howley), live near the woods, far beyond the edge of town. Though they still have their accents, Moria, now a lawyer, does not. Bonnie comments that Moira’s childhood nickname, “Twiggy,” is no longer appropriate.

Bonnie and William are in a current marital feud—set off by Bonnie having had an affair. More surprising is that, at 62 years old, she’s also had a baby. Moira’s childhood bedroom, which previously housed William’s collection of old newspapers, has been turned into a nursery, but Moira is less concerned about sleeping on the couch than Bonnie forbidding her from seeing the baby, named Maeb, after Moira’s sister who died as a teenager from a hard-to-diagnose illness. Bonnie claims it’s reincarnation. Meanwhile, William, feeling displaced in his own home, marks his territory by urinating in mugs strategically placed around the house.

When her parents claim Maeb is crying, Moira hears nothing. Late at night, Moira sneaks off to find out what is in the bassinet: The reincarnated Maeb is a life-sized doll, made from a bundle of twigs, grasses, fronds, and pine needles wrapped in yarn. For Moira, the horror is not just that Bonnie and William have become delusional, resentful hoarders whose shouting matches escalate to breaking plates. It’s that, only after leaving home and learning typical behavior and emotional responses, can Moira recognize that her parents were always like this. There is a mystery to uncover, but it is as much a matter of failing mental health that precipitated the family’s descent into madness as it is a matter of who did what.

Aside from being immersive, Simone Schneeberg and Dan Remmers’ set design cleverly uses sliding panels hanging from tracks in the ceiling to create other rooms, accentuating the haunted atmosphere of the Lane house.

In this production of an otherwise naturalistic horror story, there is nonetheless an element of the supernatural, personified as an Elemental of earth and vegetation played by Sea Griffin. First appearing at the close of the first act, it lurks in the shadows, never uttering a word: Has it been driving the family’s towards madness for decades? Did their misery lure it into their home? Or is it just a shared delusion hiding in their peripheral vision? Only when the lights go up for the actors to take their bows does the Elemental come into view. Alongside the quotidian dress of the Lane family, something resembling the Green Man of European folklore—or perhaps the Marvel Comics monster, Man-Thing—stands, wonderfully crafted by costume designer Stephenie Yee.

Spears is not just an actor and director, but an actor’s director who elicits intense performances out of her castmates and herself: The stage blood and piss might be fake, but the sweat is real. This immersive production is so committed to the visceral naturalism of Antone’s script that I was often surprised that I did not detect the odors of rot and bodily fluids. In sticking with the play’s naturalism, it’s hard to tell where her direction ends and assistant director Mundy Spears’ fight choreography begins.

Twigs & Bone, by Tiffany Antone, directed by Lynn Sharp Spears, runs at Caos on F, 923 F St. NW, through June 25. nusass.com. $30.

Some shows will feature an alternate cast of Katie Wicklund (Moira), Melissa Robinson (Bonnie), Kim Curtis (William), and Ellie Nicole as the Elemental.