Laura Hoff, an only child, is a reclusive young woman who lives with her mother, Mari Hoff, in a working-class home in Scarborough, Yorkshire, England. She is known as LV (short for Little Voice) because of her soft, shy, and childlike speaking voice. She flees reality, hiding away in her bedroom, listening to records and impersonating the voices of American and British artists such as Marilyn Monroe, Gracie Fields, Judy Garland, and Shirley Bassey; her love of songs is her only source of strength since her beloved father's death. Her mother, by contrast, is a loud and promiscuous woman with little sympathy for LV's retiring nature or her grief.
Billy, a shy and awkward telephone engineer who raises homing pigeons, meets and bonds with LV when he installs a new telephone line in Mari's apartment. Their quiet romance is interrupted when Mari brings home Ray Say, a down-and-out talent agent. Ray Say, on the lookout for an act to carry him to fame and fortune, hears LV's impressions and recognizes her gift. He vows to make her a star despite LV's reluctance to step onstage. Although Mari remains dismissive of LV's skills, she is infatuated with Ray and goes along to win his approval.
Ray arranges for LV to sing at a club owned by local comprimario Mr. Boo, but her performance is a failure as she is overcome by stage fright and only sings a few lines after Ray turns off the stagelights. Ray sees that LV needs encouragement on stage and works with Mr. Boo to organize a big band, lights, and a new dress to give her confidence, selling his car and taking out a loan from a local mobster to pay for the concert.
Ray gives her a pep talk, manipulating her into performing by portraying her act as a tribute to her father. LV agrees to sing again, but only as a one-off. LV envisions her father sitting in the club as she performs; she brings the house down and is a storming success. Ray spots a talent scout for a London agent in the audience and convinces the Agent to come and see LV perform the following night. As Ray, Mari and Mr. Boo toast their future success, LV murmurs that she agreed to sing only one time and slumps to the floor.
The following night LV catatonically remains in her bed. She ignores Mari's attempts to shame her into performing, and when Ray tries to first cajole than threaten her, she uses her impressions to scare him away. Ray, furious at losing his meal ticket, lashes cruelly out at Mari and storms away. At the cabaret club, the London agent finally loses patience after several third-rate acts fill the time in LV's absence and leaves. Ray storms into the club, grabs the mic and sings "It's Over" in a furious, profanity-laden tirade, as his career disappears before everyone's eyes, as the loan shark appears to demand his money back.
Meanwhile, the faulty wiring at LV's home finally starts a fire, trapping LV in her upper room where she is rescued by Billy. When she returns home, she discovers Mari has destroyed her fathers' records in revenge. In a final showdown with her mother, after being wrongly accused by her mother of arson, LV responds by screaming in her mother's face. Blaming her for her father's death and blaming her own meek nature on Mari's domineering attitude, she walks away saying her name isn't Little Voice, it's Laura. Freeing herself from others' control, she joins Billy to care for his pigeons and watch the sun rise.
