Cherie Currie (Dakota Fanning) is a teenager in Los Angeles, California who desperately wants to be a rock star. She idolizes David Bowie and cuts her hair and dons make-up so she will resemble Bowie's character Aladdin Sane. At her high school talent show, she lip syncs to "Lady Grinning Soul" and, despite some hecklers in the audience, wins.
Joan Jett (Kristen Stewart) is a teenager who also dreams of rock stardom. At a club one night, she meets record producer Kim Fowley (Michael Shannon) and talks about starting an all-girl rock band. Kim is interested. He introduces Joan to Sandy West (Stella Maeve), a drummer. Joan and Sandy become friends and start jamming when Kim suggests that they recruit a hot blonde in the vein of Brigitte Bardot.
Kim and Joan comb Los Angeles' clubs to look for hot blondes and discover Cherie. They invite her to audition at a trailer park in the San Fernando Valley and to prepare a Suzi Quatro song to perform at her audition. Cherie learns Peggy Lee's "Fever" instead and goes to audition, but the band is disappointed at her choice of song. Kim and Joan then write "Cherry Bomb" on the spot for Cherie to audition with. Cherie sings it and, after improving, is part of the band, named the Runaways, joined by Lita Ford (Scout Taylor-Compton) on lead guitar and Robin (Alia Shawkat) on bass. (Robin is a fictional character created for the movie as a composite of the group's multiple bass players [5 overall and 3 during Cherie Currie's time with the band]).
The Runaways are soon signed to Mercury Records and release an album. Due to the album's success, they travel to Japan to play a concert. After their performance, Lita throws magazines at Cherie that have pictures of her. Cherie is shocked because she thought the articles were to cover the whole band. As Lita, Cherie and Joan argue, overenthusiastic fans break through the window and chase the girls out of the building. Cherie's drug problems worsen. She overdoses in the hotel, collapses in an elevator and is sent to the hospital. Upon arriving back in the United States, Cherie begins to abuse her alcoholic father's painkiller medication.
At the studio recording their next album, Cherie has a mental breakdown and refuses to play. Lita insults her, and though Joan defends her, Cherie quits the band. Joan is outraged, and the Runaways are finished. Cherie returns home while Joan starts her own band, Joan Jett and the Blackhearts. Cherie collapses again in a phone booth in a supermarket parking lot. At the hospital, her twin sister Marie Currie visits her and tells her to straighten herself up.
A few years later, Cherie is working in a bakery and hears Joan's cover of "I Love Rock 'n' Roll" on the radio and calls the station, where Joan is visiting for interviews. After an awkward conversation between Joan, Cherie, and radio host Rodney Bingenheimer (Keir O'Donnell), Cherie says her goodbyes and continues working, smiling when Joan's next song, "Crimson and Clover", comes on the radio.
What song does Cherie learn for the audition?
Fever