The high-stakes struggle of a working mom with the world's most deadly job to maintain her work-life balance! To the outside world, she is an ordinary 5th-year homemaker with a husband and a 4-year-old daughter. Behind closed doors, however, she is a legendary assassin for a secret organization that executes heinous criminals who slipped through the law. This thrilling action-drama follows her perilous double life as she fights to keep her identity hidden from her news-reporter husband, who is hot on her trail. After a 3-year maternity leave, Bona returns to fieldwork under the cover of "Sales Team 3 at Durumi Electronics." Her high-wire act begins: taking down targets by day, and tackling housework and parenting by night. But her peaceful domestic routine does not last long. Tensions reach a boiling point when her husband, Tae-sung, is assigned to investigate the elusive assassin known as "Kingfisher." Determined to safeguard the precious family life she fought so hard to build, a fierce battle of wits unfolds between a wife hiding her identity and a husband determined to uncover the truth.