Elena Kensington is a picture of aristocratic perfection. Raised by the wealthy Kensington family, she is meek and ladylike, always aiming to please her ambitious parents. Despite feeling trapped in her engagement to Anthony Bridgerton, a modern-day viscount, Elena resigns herself to the arrangement. However, deep down, she dreams of a different life.
Eleanor Hayes, Elena's identical twin sister, lives a starkly different existence. Adopted by a loving single mother in the suburbs, Eleanor is outspoken, brash, and fiercely independent. She works multiple jobs to support her terminally ill mother, Linda Hayes, who is her world.
One fateful night, Elena decides to take control of her life. She flees the Kensington estate, leaving behind a note explaining her need for freedom. In a panic, her parents, Lord Edward and Lady Victoria Kensington, concoct a desperate plan. They track down Eleanor, offering to pay all of Linda's medical bills in exchange for Eleanor impersonating Elena until they can locate her.
Initially resistant, Eleanor agrees, driven by her love for her mother. She is thrust into a world she despises, forced to mimic Elena's reserved demeanor while grappling with the guilt of deceiving Anthony.
Meanwhile, the ever watching eyes of Lady Whistledown keeps the wealthy families of Aristocratic London in check.