Seventeen-year-old Kang Junhwi, who can see ghosts, loses his memory after an accident. After passing the grim reaper's challenge to win another chance at life, he is thrust into the underworld to live as an intern Hwarang, or Flower Knight. Junhwi is assigned to partner up with Horan, a peace officer partner, as they take on a series of investigations under the supervision of Bihyeongrang. Magicians, monsters, and legendary figures come into play in the mythical underworld. But what will be revealed when Junhwi investigates the circumstances of his own fateful accident?