Dae-ho is a young investigative journalist and single father who has made a few enemies by exposing several corrupt politicians and businessmen. One day, his son is abducted but no ransom is demanded. Dae-ho is convinced it is an act of revenge by one of his enemies who he exposed.
Three years pass and there is no development in the case. Dae-ho then learns of a new form of therapy that allows mental patients to relive important memories through lucid dreams. One of the physicians who administer the therapy is Dae-ho's old friend, So-hyeon.
Together, they explore Dae-ho's memories of that fateful day and find a new trail in his lucid dream. Detective Song, who was responsible for the case three years ago, decides to help Dae-ho and So-hyeon uncover new evidences.
When they uncover the prime suspect of the abduction, it turns out that he has been in a coma. Dae-ho then tracks down a mysterious teenager who keeps appearing in all his dreams. This teenager has invented a way to enter the dreams of others. Dae-ho enters the dream of the prime suspect and learns the truth.
