A young woman named Savannah Knoop spends six years pretending to be the celebrated author JT LeRoy, the made-up literary persona of her sister-in-law.

Novelist Laura Albert (Dern) writes as her "avatar", a disenfranchised young gay man named J.T. LeRoy. When her debut novel becomes a best-seller and J.T. becomes the darling of the literary world, she enlists her boyfriend's androgynous sister Savannah Knoop (Stewart) to act as J.T. in the public eye. Together, they embark on a wild ride of double lives, infiltrating the Hollywood and literary elite, and discovering who they are while pretending to be someone else.