James Pope has grown up in an isolated, underground bunker with his parents, watching episodes of a children's show called Brigsby Bear, which is made specifically for him. Unbeknownst to him, he has been living in a fake world created by his "parents," who are actually his captors. When the authorities find and rescue James, he is introduced to the real world, where he struggles to fit in and cope with his new reality. He discovers that Brigsby Bear was a fabrication and the show never existed outside the bunker.

Determined to bring closure to his childhood, James decides to finish the story of Brigsby Bear himself, enlisting the help of new friends and family he meets along the way. Through this creative endeavor, he learns about forming real human connections and confronting the complexities of his past. His journey becomes a path of healing and understanding, as he grapples with the collision of his sheltered upbringing and the broader world outside. James' dedication to completing Brigsby's story helps him find meaning and purpose in his newfound freedom, revealing his resilience and unique perspective on life.