A woman named Go Ae-Rin loses her husband. Along with her neighbour Kim Bon, who is a NIS agent, they discover the truth behind her husband's involvement in a huge conspiracy.

Chun Jae In is an elite detective with a genius IQ, who guided by only facts, logic, and numbers. Meanwhile, Kim Dan is a rookie detective who can see ghosts. They work together to uncover a conspiracy involving a powerful organization.

A young girl named Hye-Na is abused by her mother, Ja-Young. Although she is not okay, she tells other people she is alright. Soo-Jin is a temporary teacher at the elementary school where Hye-Na attends. Soo-Jin is aware of her situation and decides to become her mother.