It’s a thin line filmmakers must walk when depicting mental illness in a movie. The line is thinner when the genre you’re working in is a romance, one that flirts with being a romantic comedy. The risk is, that you’ll cross over into “cute,” and there’s nothing cute about being mentally ill, or coping with someone who is in your life.

The Aussie romance “I Met a Girl” doesn’t get into much trouble, in that regard. We meet our schizophrenic hero — Devon — just as he’s decided to forgo his pills and quaff a few. I mean, it’s his brother Nick’s wedding day and Devon’s written a song that he and his band, And They Said it Wouldn’t Last, are performing.

He wants to “be there,” right? The song is charming, and boy-band handsome Devon (Brenton Thwaites of the last “Pirates of the Caribbean” movie) pulls it off with ebullience and talent.

But as they do, things go manically, violently wrong and Devon winds up in a hospital.

“I was twelve when I first hear the voices,” he narrates. We have our diagnosis, and the scope of Devon’s problem. Being beautiful and talented doesn’t inoculate you against schizophrenia.

Five years later, and he’s living with Nick (Joel Jackson) and his expectant, tolerant wife Olivia (Zahra Newman). But Devon is still dodging his pills, when he can. Manic episodes mean he can’t keep a job. Working at a pet store, he reacts to a born-bully/animal abusing kid by flipping out and freeing all the budgies.

He totes his guitar everywhere, but he can’t get the band back together.

“Time to grow up, mate,” they tell him.

And the two voices in his head prey on him when he’s unmedicated and having a bad day. Mr. Rocket is a superhero “protector” who pushes him into risks. Miss Needle is a Nurse Ratched menace, terrorizing him with injections, tormenting him over his failings.

They drive him up on a roof and off it.

Only he doesn’t die. He wakes up in a beautiful woman’s clawfoot tub. She “dragged” him there, she says. Her name is Lucy (Lily Sullivan of TV’s “Picnic at Hanging Rock”). She’s flirtatious, kind, open and direct.

“Like, were you trying to kill yourself?”

She has one of those glorious “only in the movies” flats that nobody whose employment is dressing up like Marilyn Monroe as a waitress for a ’50s themed diner. She drops everything she’s doing to spend the day with Devon, and they fall in love in a flash.

We think it long before he says it. “It’s like I’ve dreamt you.”

Is she all in his head, a fantasy that his mind has created to fill one of the many voids in his life? We’ll know when joins Nick and Devon for dinner. Only she doesn’t show up.

Her flat is empty. And real-estate agent Nick, with a baby on the way, has no patience for Devon’s mad fantasy.

“She’s as real as you and I” isn’t convincing.

But Devon has a clue, and on or off his meds, he’s going to pursue it. He’ll leave Perth and cross Australia to Sydney and find his Lucy. And on or off his meds, he’ll have adventures all along the way.

Filmmakers Luke Eve and Glen Dolman, Aussie TV veterans, come up with a few cute episodes for Devon’s trek, and a few harrowing moments as his demons literally chase him cross country, with frantic Nick trying to figure out where his crazy kid brother’s gone.

Visualizing Devon’s illness — with actors playing his two “voices” — is a lot less scary than aurally simulating what’s going on in his head. But taking care to never let us forget the seriousness of his condition shortchanges the “cute” encounters he has on his “road comedy” journey.

Meeting someone just like himself is a plus, but the other meetings are hit and miss.

Thwaites, who apparently does his own singing, has to carry the picture with his charm, and he almost does. He’s charismatic and cute and doe-eyed in his scenes with Sullivan, who seems older (she isn’t), world weary and wiser.

The players give “I Met a Girl” a warm and fuzzy romantic lilt. But the best one can say for the script is that it gives the charming stars a nice moment or two, and that it generally doesn’t fall for the “Love can cure what ails you” mental health rom-com trap.

Every now and then? Sure. But “generally,” no. Take your meds and hope for the best. Male wish fulfillment fantasy girlfriends are only in the movies.

MPAA Rating: unrated, adult situations, violence

Cast: Brenton Thwaites, Lily Sullivan, Joel Jackson, Zahra Newman

Credits: Directed by Luke Eve, script by Glen Dolman. A Gravitas Ventures release.

Credits: 1:48