Annie Baker must love losers. In “The Flick,” this never-dull and consistently surprising scribe observes the aimless lives of three movie theater ushers with sharp insight and grave tenderness. Her compassion extends to the theater itself, a seedy second-run house with one of the last 35-millimeter film projectors extant in the state of Massachusetts. Baker and long-time collaborator, helmer Sam Gold, have been hot to the touch since “Circle Mirror Transformation.” And while they take their signature hyper-naturalistic style to extremes here, they’re still turning out must-watch work.

Like the rural Vermont slackers Baker captured so eloquently in “The Aliens,” the three co-workers in “The Flick” are headed for nowhere if they don’t break out of zombie mode. That seems unlikely in the case of Sam, the 35-year-old head usher played with unnerving honesty and not a trace of condescension by the amazing Matthew Maher.

When the lights go up on the shabby movie theater, designed with depressing accuracy by David Zinn, Sam is robotically making his way through the house, moving from aisle to aisle, sweeping up popcorn and mopping spilled soda off the floor. His efficient movements and agreeable manner indicate that Sam takes genuine pride in his dead-end job.

Sam seems mystified by Avery (Aaron Clifton Moten, a talent-and-a-half and a real find), the young college kid he’s training in the job. Avery’s impassive expressions and monosyllabic responses make communication heavy going for the garrulous Sam. But the ice is finally broken between these two cinephiles over a killer game of Six Degrees of Kevin Bacon.

Baker is strictly of the show-don’t-tell school of playwriting, so she stays clear of confessional arias. Instead, she comes at her character revelations in more oblique ways: in the guarded exchanges of friendship between Sam and Avery, and especially in their relationship with the green-haired projectionist, Rose, a free spirit whose defiant independence asserts itself in a wonderfully inventive, up-yours perf by Louisa Krause.

She’s a handful, Rose is, and Sam is sweetly and pathetically in love with her. But Rose puts the moves on Avery, who is terrified of her, as anyone would be who is exposed to the manic mating dance she performs when she gets Avery alone. And insofar as this slice-of-life material has a plot, it hangs itself on this romantic triangle.

But it’s character, not plot, that fires the engine of this show. You do have to like movies to work in a movie theater, as both Sam and Rose do; but Avery is a bona fide film snob. Baker gets real belly laughs just from polling these three on what constitutes a “great” American movie. Earthbound Sam picks the metaphysical fantasy “Avatar,” while scrappy Rose goes for “Million Dollar Baby.” Avery, the indulged child of rich parents, reveals a rebellious side when he chooses “Pulp Fiction.” Like the idiomatic dialogue that Baker nails with devastating accuracy, film tastes help define people and what they expect from the movies — and from life.

It’s the dramatic intention of this savvy scribe to convey, in something like real time, the stultifying, stupefying, brain-eating boredom of the no-exit lives these alienated young people are trapped in — and by extension, the limitations of the world outside the theater where they’ve found temporary refuge. But it doesn’t take three hours to accomplish this, and after the first two hours, it feels like self-indulgence.

The Flick

Playwrights Horizons; 198 seats; $70 top

A Playwrights Horizons presentation of a play in two acts by Annie Baker. Directed by Sam Gold.

Set & costumes, David Zinn; lighting, Jane Cox; sound, Bray Poor; production stage manager. Alaina Taylor. Opened March 12, 2013. Reviewed March 7. Running time: THREE HOURS.

Sam — Matthew Maher

Avery  Aaron Clifton Moten

Rose  Louisa Krause

Skylar  Alex Hanna