TWICE, a group under Seoul's Secret Service (SSS or S3) led by Jihyo, was sent to an operation to save the laburis. The operation was a success and TWICE was disbanded afterward. Years after the incident, a series of events led the members back to each other. A terrorist attack led to a member's disappearance. Jihyo, the only active member left from TWICE to serve the SSS, was tasked to find the missing member. However, it seems like the task is too daunting for her to handle.
Twice work together at the Police Force when they suddenly get a new member joining them. A young girl with smarts named Lena, and as the youngest, Twice look out for her. They got assigned a new case, but have the hardest time finding out who is the suspect. What would happen if the suspect actually works with them?