Naoko and Monami, mother and daughter, are in a bus accident. Naoko dies, but her spirit ends up inhabiting Monami's body. She then returns home to Heisuke, dad, and they try to figure out how to live their lives. Additionally, there is some suspicion surrounding the cause of the accident, which Heisuke investigates. ~~ Adapted from the 1998 novel "Himitsu" by Higashino Keigo.