In 1969, child prodigy William Miller struggles to fit in. His life is further complicated after learning that his widowed college-professor mother Elaine has falsely led him to believe he is twelve years old. William is actually eleven, having started the first grade at five years old, and skipping fifth grade. Strong-willed Elaine’s strict ban on rock music and pop culture influences that she fears have a negative effect on her children finally drives William’s eighteen-year-old sister Anita to move to San Francisco and become a flight attendant.
In 1973, William, now fifteen, influenced by Anita’s secret cache of rock albums, aspires to be a rock journalist, writing freelance articles for underground papers in San Diego. Rock journalist Lester Bangs, impressed with William’s writing, gives him a $35 assignment to review a Black Sabbath concert. William is barred from backstage until the opening band Stillwater arrives and William flatters his way in. Lead guitarist Russell Hammond takes a liking to him and his new acquaintance, veteran groupie Penny Lane, who has taken William under her wing. Despite behaving as stereotypical groupies, Penny Lane insists she and her friends are “band aids”, a term she apparently invented to describe female fans that are there for the music and less so for the rock stars themselves.
Rolling Stone editor Ben Fong-Torres, believing William is older, hires him sight unseen to write an article about Stillwater and sends William on the road with the band. William interviews the members, but Russell repeatedly puts him off. Tensions between Russell and lead singer Jeff Bebe soon become evident and not helped at all by the band’s first tee shirt, a full band shot that pictures Russell in full view while the rest of the band is virtually in shadows. William is jokingly called “the enemy” by the band because he is a journalist, but all the same begins to lose his objectivity as he becomes integrated into their inner circle.
The band’s record company hires Dennis, a professional manager, to handle problems with venues and promoters. Penny has to leave before the band reaches New York, where Russell’s girlfriend Leslie will join them. Penny and her three protégée band aids are gambled away to another band in a poker game; Penny acts nonchalant but is devastated. Meanwhile, Dennis charters a small plane so the band can play more gigs.
Penny shows up uninvited at the New York restaurant where the band is celebrating the news that they are to be featured on the cover of Rolling Stone. Penny is asked to leave after Leslie notices her attempts to get Russell’s attention. William chases her to her hotel, where he saves her from overdosing on quaaludes.
While flying to another gig the following day, the band’s plane encounters severe weather. Believing the plane will crash, everyone confesses their secrets, while Jeff and Russell’s long-simmering conflicts erupt. William defends Penny after Jeff insults her and confesses he loves her. The plane lands safely in Tupelo, leaving everyone to ponder the changed atmosphere.
William arrives at the Rolling Stone office in San Francisco but has difficulty finishing the article. Seeking help, he calls Lester Bangs who says William got caught up in being part of the band. He says William’s perceived friendships with them are not real and advises him to “be honest…and unmerciful.” Rolling Stone’s editors rave over William’s completed article, but when the magazine’s fact checker calls the band, Russell lies to protect Stillwater’s image and claims 90% is false. Rolling Stone kills the article, crushing William. Anita encounters a dejected William in the airport and offers to take him anywhere; he chooses for them to go to their home in San Diego.
Groupie Sapphire chastises Russell for betraying William. Russell calls Penny at her home and wants to meet with her, but she tricks him by giving him William’s address. He arrives and finds himself face-to-face with William’s mother, who scolds him for his behavior. Russell apologizes to William and finally gives him an interview. Russell has verified William’s article to Rolling Stone, which runs it as a cover feature. Penny fulfills her long-standing fantasy to go to Morocco while Stillwater tours again by bus.