Choi Byung-mo

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.

Chinese secret agent Da-hee receives intel that a large number of illegal firearms are being smuggled into Korea and is sent to investigate the case. She meets Su-han, who is supposed to help her with the case, but due to his lackluster skills they fight over trivial things. But as their witnesses are suddenly murdered, the two of them quickly become the prime suspects.