Yu Bona is no ordinary mom returning to the office after maternity leave. For her first assignment back she heads to a rooftop, points a sniper rifle at her target in a nearby hotel room, and "bang!" the legendary assassin "Kingfisher" is back. But as Bona takes on a series of new targets, her news reporter husband Taesung is ordered to investigate Kingfisher's return, and as the bodies pile up, the line between personal and professional slowly starts to blur.