Tells the story of married couple Eun-su and Ho-jin, whose younger brother Dae-jin also lives with the inseparable pair. Dae-jin is carefree but behaves erratically. Seemingly they enjoy the perfect life, until their tranquil world comes crashing down around them when tragedy strikes one fateful day as two separate car accidents put both brothers in a coma. Only the younger sibling wakes, leaving Eun-su to restart her life alone without her husband. Left disorientated, events take a strange twist as Dae-jin's behavior changes, beginning to resemble that of Ho-jin, leaving everyone familiar with his antics questioning his peculiar mannerisms. Through the trauma and hysteria, Dae-jin believes he is in fact his brother and that he is possessed. Eun-su is left to wonder if her husband's soul is trapped in the body of her brother-in-law or if he's just mentally unstable.