Too many character neuroses can spoil a good play. A leading man who repeatedly quotes It’s a Wonderful Life, for example, might be charming, but not one who channels Jimmy Stewart, takes lots of Polaroids, celebrates every holiday, and pontificates about Abstract Expressionism.

Writing plays about the socially awkward should be a foolhardy enterprise, yet that’s what Sarah Ruhl tends to do, and she won a 2006 MacArthur Genius grant for her efforts. In 2007, Woolly Mammoth hosted the premiere of Dead Man’s Cell Phone, Ruhl’s postmodern oddball comedy about 21st century communication. Late: A Cowboy Song is a few years older, and it feels like an example of an untamed genre-in-the-making, despite this excellent staging by No Rules Theatre Company, an ambitious young troupe in residence at Arlington’s Signature Theatre.

Chris Dinolfo and Sarah Olmsted Thomas star as Crick and Mary, grade-school sweethearts now living a Stepford-like existence as adult lovers. When one antagonizes the other, they both pause and reach for the same imaginary ache at the nape of their necks. And they antagonize each other quite a bit, exchanging jabs in a manner that makes Thomas sound like a likeable automaton and Dinolfo a petulant child.

“Do you have any money?” Crick asks her, like they’re still in second grade and he lost his allowance. “Why?” Mary says, adding that she has a little. “Can I have some?” he says.

To escape the bickering, Mary reconnects with a former classmate named Red, who was most memorable because she wore red velour pants and carried a money clip instead of a purse. The grown-up Red is a cowboy who specializes in singing horses to sleep. The show is set in Pittsburgh.

These are the sort of idiosyncrasies Ruhl expects audiences to run with, and the only way she gets away with it here is that as Red, Alyssa Wilmoth is an extremely convincing cowboy. Clad in Carhartt, she responds to Mary’s ramblings with monosyllables, or a simple, “I reckon so.” Wilmoth’s recent roles in D.C. include the unstable, overly social psychologist in Becky Shaw at Round House, and this contrasting No Rules performance indicates she has pretty amazing range, both when acting and singing.

In the play’s most sincere moments, Wilmoth is onstage with a guitar, and she’s not just strumming. Her voice says look out Kacey Musgraves, and she plays guitar like she didn’t learn in rehearsals last week. (The lyrics are Ruhl’s, but the music is a collaborative effort by singer/songwriter Kinsey Charles and director Rex Daugherty. The entire show benefits from high-quality sound design.) As she sings, Mary and Crick are at stage left, usually engaged in some sort of movement sequence. The birth of their child is depicted as a pas de deux à la Martha Graham, and the sex scenes are just as elaborate.

The dramatic conflicts deal with whether Mary will leave Crick to start a romance with Red, what sex they should choose for their intersex child, and whether Crick was wrong to spend their savings on a painting. That’s enough tension for one show, but because Mary and Crick need therapy for so many obsessions, it’s hard to care about them as characters also facing plot-driven problems. Mary’s hobbies include calling her mother, writing in her diary, and learning to cook clear Chinese soup. Maybe Ruhl did a little too much research about OCD. Late may be a postmodern fairy tale about a housewife who married young and longs to fulfill her dreams, but the classic fairy tales have uncomplicated heroines, making it easier to believe in cursed spinning wheels and seven dwarves. Like cowboy ditties, sometimes good stories are best kept simple.