In her 1960s heyday, the British pop tart Marianne Faithfull recorded a few hits, had a stormy affair with Mick Jagger, spun the revolving door of detoxification a few times, and graced her share of tabloid headlines. Her iconic presence leaped onto the big screen as well, notably with appearances in cult films by Jean-Luc Godard and Kenneth Anger. Ms. Faithfull is also, according to many, the first person to ever utter the four-letter “F” word in a major motion picture — in her movie debut, no less, alongside Orson Welles and Oliver Reed in “I’ll Never Forget What’s’isname” (1968). The irony of her latest starring role, four decades later, is unlikely to escape her devotees.

In “Irina Palm,” which opens Friday at the Quad Cinema, Ms. Faithfull plays Maggie, a mousy widow whose life has come to revolve around her gossipy bridge club and hospital visits to her very ill grandson, Olly (Corey Burke). Rather than sit and watch as tears go by, Maggie, in a desperate attempt to finance Olly’s imminent surgery, applies for a position as a hostess at a sex club in London’s seedy Soho district. Thinking (preposterously, one might add) that the job would entail serving tea and biscuits, Maggie shudders to discover that she instead has to pleasure customers through a hole in a wall (reconsider the title). In spite of her reluctance, the money is simply too good to turn down. Maggie, as it not so surprisingly turns out, has a knack for her job, and her greatest obstacle becomes evading the curiosity of her family and friends as the cash starts rolling in.

Aside from her fascinating offscreen personal history, Ms. Faithfull brings little to her role. Perpetually unemotive, she seems to have really weathered from her intrepid days in “The Girl on a Motorcycle.” It’s as if the purpose of this stunt casting is to prove how time can be so unkind, which is especially unfortunate, because the role screams for a much better actress. Brenda Blethyn would have made a good fit.

Screenwriters Martin Herron and Philippe Blasband seem to have in mind a British-centric comedy that follows the formula of “Calendar Girls” or “The Full Monty,” in which frumpy, working-class people resolve their financial crises by pulling a spectacular, taboo-tinged feat. Curiously, director Sam Garbarski directs their script with gloomy compositions and gritty ambience, offering the same dark version of London that David Cronenberg used to great effect in “Eastern Promises.” The comedy is still there — such as Maggie wearing an apron to work and decorating her cubicle with plastic flowers and pictures from home — but the humor comes off as deadpan rather than side-splitting. At times, it feels as though Mr. Garbarski needs to lighten up, given that the screenplay is just too full of gaping holes — logistic and otherwise — for anyone to take his film that seriously.