Ramona Edith-Williams, left, and Kelly O’Sullivan in “Saint Frances.” (Oscilloscope)
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Rating: (3 stars)

Watching the opening scenes of “Saint Frances,” it’s tempting to steel yourself for yet another parable about the Youth of Today: a vaguely tolerable millennial protagonist dealing with a dash of ennui here and a sprinkling of existential angst there.

But wait! There’s a sassy tot who will give the protagonist a newfound purpose in life.

Instead, what emerges from the feature debut of director Alex Thompson and writer Kelly O’Sullivan (who also plays the main character) is a charming, nuanced story with plenty to say about making just that sort of superficial judgment and about what people are actually going through beneath their carefully crafted appearances.

O’Sullivan plays Bridget, a 34-year-old aimlessly waiting tables before bouncing to an equally uncertain seasonal babysitting job. Her charge: precocious 6-year-old Frances, played by Ramona Edith-Williams, who shines, in her first role, like a tiny ball of light. From Bridget’s irony-tainted point of view, Frances’s parents, Annie (Lily Mojekwu) and Maya (Charin Alvarez), are a couple of well-off, milquetoast liberals — the kind with a “Hate Has No Home Here” sticker affixed to their front door.

Bridget appears to be the apathetic slacker familiar from so many breathless blogs. Her one-night stand with a 26-year-old schlub — whose heart is in the right place — turns into a series of unidentified hangouts and hookups, all of which lead to an unplanned pregnancy. This is discovered, charmingly, after Bridget, loaded down with an armful of Cookie Crisp cereal, chocolate milk and wine, mentally calculates that her period is late and reaches for a pregnancy test.

Ramona Edith-Williams in “Saint Frances.” (Oscilloscope)

Thompson and O’Sullivan bring sensitivity and an observant touch to the weighty proceedings: There’s no overwrought hand-wringing when Bridget decides to get an abortion, simply an assurance that she is in control of her life.

But it’s the push-and-pull between Bridget and Frances that is the poignant heart of the film. Sure, Bridget could stand to grow up a bit. But we never feel like she’s coasting. If she’s dealt herself a bad hand — along with a few self-inflicted wounds — she’ll deal with it. Frances, for her part, is a little scamp, ever so gently pushing the boundaries of what her babysitter will tolerate. By the end, the authenticity of their bond feels so well-earned that you might not mind watching another movie about them growing up with each other.

In an otherwise succinct tale, O’Sullivan’s script wobbles when the focus shifts from that dynamic. Bridget’s dalliance with a ­music teacher feels shoehorned into the story as a way for her to learn a lesson of some kind — but what that lesson might be, exactly, isn’t clear. As for Annie and Maya, their characters don’t become three-dimensional until late in the film — a welcome gesture toward the questions we’d rather leave unspoken about bringing life into the world — but the transformation feels rushed.

The movie’s title is a vague nod to Bridget’s faith — she’s a lapsed Catholic — but its meaning doesn’t resonate quite as powerfully as the film’s central relationship. That yarn is a promising indicator that Thompson and O’Sullivan may yet have more stories to tell us about our capacity to grow and to treat each other better.

Unrated. At the Avalon Theatre. Contains mild language and some mature thematic material. 106 minutes.