The story unfolds with Brian Wilson, a creative genius and leader of the Beach Boys, struggling with internal demons during the 1960s. His innovative approach to music brings the band significant success, but it takes a toll on his mental health. As he composes the iconic "Pet Sounds" album, Brian's mental state deteriorates, leading to a breakdown that impacts both his professional and personal life. The film alternates between this period and a future timeline, exploring Brian's attempts to navigate his turbulent mind while contributing groundbreaking work in the music industry.

In the 1980s timeline, an older Brian is under the strict control of Dr. Eugene Landy, a manipulative therapist who exerts immense influence over his life. During this period, Brian meets Melinda Ledbetter, a car saleswoman who becomes a beacon of hope for him. As their relationship develops, Melinda becomes increasingly aware of Landy's oppressive grip on Brian and strives to free him from it. Her unwavering support and determination lead to a series of confrontations with Landy, aiming to restore Brian's autonomy and well-being. The narrative weaves between these two eras, highlighting the stark contrasts in Brian's journey and his enduring resilience amidst adversity.