Plot summary

The film alternates between the 1960s and the 1980s. The early timeline begins with a young Brian Wilson (Paul Dano) suffering a panic attack on an airplane. It is agreed with the rest of The Beach Boys that Brian will no longer tour with them and will instead focus on composition and studio work. Despite resistance from some of his bandmates, Brian completes the "Pet Sounds" album. It is a critical hit, but sales are underwhelming. LSD is supplied to Brian by a coterie of hippie vagrants who praise him as a "genius", and his mental health subsequently worsens. After the success of a new single, "Good Vibrations", he fails to complete the album "Smile," his would-be masterpiece. As Brian's bandmates record their next record without him, he learns that his father has illegally sold the publishing rights to the Beach Boys' songs. This timeline ends with Brian apathetic and detached from life.