Abby (Robin Weigert), left, surprises her friend, Sam (Maggie Siff), with her sudden turn as a high-priced call girl for female clients in “Concussion.” (RADiUS-TWC)

Concussion” explores the phenomenon known as Lesbian Bed Death — a term coined by sexologist Pepper Schwartz to describe the drop in sexual desire and/or activity experienced by some long-term lesbian couples — through the prism of a single couple: high-powered New York divorce lawyer Kate (Julie Fain Lawrence) and her bored, sexually unsatisfied partner, Abby (Robin Weigert). It’s hardly sociology, yet as drama it’s on the dull side, despite a fair amount of tasteful, non-explicit sex.

Abby’s the protagonist, and she gets things going quickly, taking a wayward ball to the head, tossed by one of her two children, in the film’s opening seconds. That bump on the noggin leads to the titular concussion, which may or may not have anything to do with what follows. Suddenly, Abby decides to spice up her life as a suburban housewife, mother and PTA member by taking on work as a high-priced call girl for lonely female clients.

Undoubtedly, Abby’s unusual career move has more to do with the fact that she’s miserable than with her head injury. “I don’t want this,” she shouts, on the way to the emergency room, and it’s clear that she’s not talking about the accident. Still, the film’s title hints, unsubtly, that there may be a medical explanation for Abby’s abrupt behavioral change.

Frankly, it’s such a sharp left turn that a brain injury helps explain things. Nevertheless, Weigert is a good enough actress that she makes the character’s difficult transition plausible, despite a scenario by first-time filmmaker Stacie Passon that, on paper at least, seems kind of rushed.

Step one: Abby hires a “dirty,” drug-using dominatrix (Sarah Dubrovsky). Step two: Abby confesses her infidelity to her friend Justin (Johnathan Tchaikovsky), who suggests that she use a more professional contractor next time. Step three: Said contractor (Kate Rogal) reports back to Justin that Abby is “good” enough — wink, wink — to go into business for herself.

And we’re off and running, with Justin serving as her pimp and Abby setting up shop in the chichi Manhattan loft that she and Justin are renovating. Scheduling her assignations for the morning, Abby is done just in time to pick up the kids (Micah and Maren Shapero) from school and to get home for dinner in the McMansion that she shares with Kate, who still has no clue.

What’s going on here? Our heroine isn’t in it for the money; Kate’s rolling in it. And the sex, while apparently gratifying, seems secondary to the sense that Abby gets her biggest kick out of helping lost women find themselves. Her clients include an obese, 23-year-old virgin and an older wallflower for whom Abby is more psychotherapist/life coach than sex worker.

In truth, Abby should devote half as much energy to finding herself. At 42, she tells us, she’s dismayed that she still doesn’t know who she is or what she wants.

Neither do we, ultimately. Despite a talented ensemble cast and assured direction by Passon — a protege of filmmaker Rose Troche (“Go Fish,” “The L Word”), who produced the film — “Concussion” suffers from a chilly detachment that feels all too clinical, when all we want, like Abby, is connection.

★ ★

R. At the West End Cinema. Contains sensuality, nudity, obscenity and drug use. 96 minutes.