In writer-director Duncan Tucker’s feature debut, Transamerica, a pre-op transsexual named Bree discovers that back when she was an experimental college student named Stanley, he fathered a son. When Bree agrees, at the insistence of her therapist, to bail the kid out of a New York jail, she just wants to drop him off somewhere safe and get back to Los Angeles for her long-awaited transformation.

Bree, it should be pointed out, is played by a woman. Desperate Housewives star Felicity Huffman does the honors, with makeup realistic enough that it reportedly traumatized her daughter during a visit to the set. The film opens abruptly, with a shot of a young woman in an instructional video slowly bringing her voice down octave by octave. Then Tucker cuts to Bree getting dressed for the day, smiling in the mirror before she heads to her psychiatrist to get one of two signatures needed for her gender-reassignment surgery. But she lets slip that she’s received a call from someone claiming to be Stanley’s son, and Margaret (Elizabeth Peña) refuses to sign the papers until Bree deals with the situation.

When Bree flies to New York to get the attitudinal Toby (Kevin Zegers) out of the clink, Toby assumes she’s a church volunteer. Relieved that she doesn’t have to explain who she is, Bree says that she’s from the “Church of the Potential Father,” returns Toby to his decrepit apartment, and gets ready to light out for L.A. The squalor and Toby’s intention to hitch to California to become an actor soften Bree, though, so she gets a cheap car and the two head into the non-punny part of the film’s title.

Besides Bree’s still-unrevealed secret, Tucker’s version of the road trip is pretty typical: sunrises, sunsets, blindingly bright afternoons on desolate roads as the pair travel to Kentucky, where the boy grew up, and Colorado, where Bree grew up. They’re silent; they make conversation; they argue.

Tucker and Huffman—whose lowered but feminine voice and not-quite-right-carriage are terrific—make Bree not a flamboyant female impersonator but a rather proper lady. Even before she and Toby become close, Bree acts like a parent who won’t let her child get away with anything, from poor table manners to drug use, dishing out the discipline with lilting sarcasm. Dad is also constantly trying to discourage Toby from searching for his father (“I’m a loner,” Toby says in a diner. “That’s wonderful! That’s the spirit!” Bree replies), but she does bring him to visit her own parents (Burt Young and Fionnula Flanagan), who lavish attention on their grandchild without Toby’s ever knowing why.

That reunion also shows us why Bree tells people her parents are dead. Bree is a person trapped in a world much glitzier than she is, someone whose limiting circumstances include working two menial jobs and having a penis that disgusts her. The film she’s in is a lot easier to like, too, especially for its non-fairy-tale-ish take on achieving contentment: When a doctor, before he gives consent for Bree’s surgery, asks her if she’s happy, she responds, “Yes. I mean no. I mean I will be.”

TRANSAMERICA ( * * *)

Directed by Duncan Tucker. • Starring Felicity Huffman, Fionnula Flanagan and Graham Greene. • (R, 103 min.) • At the Century Cinemas Del Monte Center.