"As the threads of fate entwine our souls, we are bound together by the invisible red string of destiny, destined to find each other across time and space." In the heart of Seoul, trauma surgeon Kim Sun Young fights to save lives against the relentless march of death. When she defies fate and intervenes to save a man destined for the afterlife, her world collides with that of Park Joong Gil, a Grim Reaper bound by duty to ensure the natural order of life and death. Drawn to each other by an unseen force, they find themselves entangled in a world where one saves lives and the other takes them.