Koh Ae-rin, a mom that quit her job a long time ago, starts looking for a job to make a living when her husband suddenly passes away. While doing something no one asked her to at her new job, she finds out a secret of the Korean office of Cornerstone, an international military industrial complex. She gets involved with Kim Bon, the man next door that has been chasing after a huge conspiracy and involuntarily becomes a member of Kingsbag, a special organization within the National Intelligence ServiceNIS. She grows rapidly within the world of intelligence, which had seemed like a totally different world to her, and shows great performance that even surprises the NIS agents.