At work, she's a renowned assassin. At home, she's a single mom to a teenage daughter. Killing? That's easy. It's parenting that's the hard part.

Jae-ho, who aims to become the number one in a crime organization, gets to build up trust with Hyun-su, an ambitious newbie in the prison. While they try to take over the organization after the prison release, their ulterior motives starts to emerge.