Following the loss of his wife in a hit-and-run accident, psychologically traumatized architect Seo Chul moves back into his parents' house with his young daughter, Ye Na, and attempts to find clues about the perpetrator through hypnosis. One day, he receives news that his long-lost sister, Yoo Jin, has finally been found 25 years following her disappearance, and she soon moves in with them too. Realizing he knows nothing of her past, Seo Chul starts feeling suspicious of her when things around the house start to change.