Juno Temple delivers a dazzling turn as an aspiring singer/songwriter struggling to protect and look out for the schizophrenic producer who “discovered” her in “Lost Transmissions.”

As Hannah, she turns manic with fear over what could become of Theo (Simon Pegg), a Brit trapped in his head and lost in America’s byzantine health care system and bizarre mental health Catch-22s. Hannah’s mania spins out of her intimate knowledge of Theo’s predicament. She’s among the medicated mentally ill herself. She understands what he’s going through and what he’s up against.

And like Theo, she is off her meds.

Katharine O’Brien’s “inspired by a true story” debut feature begins with a musical connection that cements a friendship and partnership, and then sets up its fundamental dilemma with just a line, delivered by one of Theo’s circle of friends.

“Don’t let him take you down the rabbit hole with him, Hannah.”

Theo is the life of parties within that circle. A successful record producer who used to belong to a band himself, he lures shy Hannah into a duet with him at the piano. He flirts with talk of initiating her into “a secret society.” He tempts the cubicle-drone Hannah with a trip to his recording studio, filled with instruments, some of which used to belong to legendary producer Phil Spector and Chaka Khan.

In a flash, he’s turned a song or two of hers, “written when I was a kid,” into dreamy synth-pop. In another flash, she’s set up to write tunes for a bleached dance pop bombshell (Alexandra Daddario) based on just that demo.

And then she makes the mistake of giving Theo a lift. He’s antic, and absorbed with the station between stations on her radio. “If you listen really carefully, you can hear the transmissions!”

He’s lost his car — literally misplaced it. He’s twitchy, jumpy and “off.”
“Are you ON something?” No. He’s “OFF” something.

Unlike Hannah, who “keeps everything level” with meds, Theo fears it muffles his brilliance and mutes his gifts.

He shouts “Listen, listen LISTEN” to her over the radio. A call to his friends earns a “Oh God, not AGAIN.” And in spite of all that, Hannah takes responsibility for her mentor and is even tempted to try life without medication as a jolt for her “inspiration.”

O’Brien gives Pegg scenes to show Theo’s laser focus at the mixing board as he works his mixing magic with a band. Theo is stone-faced and in-the-zone. But we can feel what’s coming. We’ve seen the hair-trigger temper, heard the unfiltered “truth” he can blurt out, giving away the crazy.

Temple, a screen veteran (“Atonement,” “Black Mass,” “Wonder Wheel”) who too-rarely lands a lead, is heartbreaking when Hannah is frantically trying to keep Theo out of harm’s way — involuntarily institutionalized for “observation,” confronting police, acting-out on a drive to the mental hospital.

She’s funny when Hannah drops her meds and starts acting out — Theo style — in her “sellout” scenes with Daddario, who is spot on as the gorgeous, nail-biting egomaniac who needs Hannah’s talent to pretend she has some of her own.

Pegg is the very picture of schizophrenia — funny and charming, here and there, lucid when he can get it together to lie to a doctor, bug-eyed and furious when Theo’s independence is threatened and his view that “time” is being controlled…by somebody — isn’t taken seriously.

O’Brien even gives us a homeless “prophet” tirade to show how common this temporal mania is among the mentally ill. Theo wears watches all over his arms and ankles.

O’Brien and her players take a common creative community belief — that “maybe the insanity makes (unusual) neuro-connections in his brain” that renders the brilliantly unbalanced brilliant — and have made a superficial but grimly realistic and thoroughly engrossing movie gloss of that theory.

And Temple has reminded us that she’s better than all those bit parts as tarts, “broads” and the like, a leading lady of formidable empathy and range. Hell, she even sings.

MPAA rating: unrated, drug abuse, profanity, violence.

Cast: Juno Temple, Simon Pegg, Alexandra Daddario

Credits: Written and directed by Katharine O’Brien. A Gravitas Ventures release.

Running time: 1:45