“Jumanji” and Marvel veteran Karen Gillan finally finds a star vehicle in sync with her brittle, awkwardly funny persona with “Late Bloomers,” a sentimental comedy about an aimless, guilt-stricken young woman who finally grows up when she takes on the responsibilities of a caregiver.

Something about the Scottish actress who usually plays Americans never quites makes a connection in much of her work. Maybe the American accent takes up too bandwidth to allow warm and witty to register. Bitchy? Touchy? Distracted? Sure.

But as pushing-30 Louise, a would-be singer between jobs who never got over that last breakup and avoiding “coming home” or even taking the many calls from her Dad (Kevin Nealon), Gillan shines, leading us on a journey from self-deluded to self-aware and self-confident to selfless.

Because that’s what it takes to devote yourself to elder care.

Rock bottom for Louise is drunkenly falling off a Brooklyn ledge, stalking the ex-boyfriend who won’t open the door for her. She’s 28, practically alone in the city and she’s broken her hip, a geriatric injury, nurses and her surgeon remind her.

The hostile old Polish woman (Malgorzata Zajaczkowska, of “Enemies, a Love Story” and “Bullets Over Broadway,” back in the day) who shares her hospital room is just icing on the misery cake.

Running into Antonina later during rehab doesn’t warm either of them up. But when the old woman who speaks no English can’t make her own way home, Louise takes her in for the night. She’s got an iPhone and translator app. If it ever works, it’ll be a cinch.

Louise ends up pitching-in to help out Antonina’s granddaughter Sylvia (Michelle Twarowska), who’d rather just drop the old crank in a home. Louise’s apartment-sharing landlord (Jermaine Fowler) is forcibly enlisted in this “job.” At least this gives her an excuse when she finally returns Dad’s calls.

Flashbacks relate how Louise learned to sing and play guitar from Mom (Talia Balsam). But Mom’s descended into dementia, Dad is desperate for help, or at least for Louise to come get some closure.

It’s going to take a lot of Antonina time to make the lovelorn Louise compassionate enough to mature from “I can barely take care of myself” to taking care of others.

Director Lisa Steen, screenwriter Anna Greenfield and Gillan go for “quirky” in this portrayal, and they succeed, giving us a clingy but off-putting character struggling to make bar pickups and have sex for the first time in “three years,” who transforms into somebody warm enough to put herself and her needs second — even if she’s still on crutches.

The narrative wanders a bit and that makes the character’s development and the story’s flow uneven and herky-jerky. Several characters are thrown in but left to wither in the final edit, and Louise’s relationships seem to suffer from narcissistic attention deficit disorder — hers and the screenplay’s.

But Gillan and Louise warm to the task, and even give us a little song as this sad-edged little comedy makes its way towards a not unexpected, warm and not wholly anticlimactic climax.

Rating: 16+, sex, alcohol abuse, scatological humor, profanity

Cast: Karen Gillan, Malgorzata Zajaczkowska, Jermaine Fowler, Talia Balsam and Kevin Nealon.

Credits: Directed by Lisa Steen, scripted by Anna Greenfield. A Vertical release on Amazon Prime.

Running time: 1:30