Cha Min, devastated after being abandoned by his fiancée Jang Hee-jin, is knocked off a roof and killed by a rogue spacecraft piloted by careless cosmic beings. To rectify their mistake, they revive Min using the celestial artifact called the 'Abyss', which reconstructs bodies in the likeness of the soul, transforming him into an exceptionally handsome man. The cosmic beings casually hand Min the marble before leaving.
Shortly after, prosecutor Go Se-yeon is murdered in her home by the Eomsan-dong serial killer. Min revives her corpse at the morgue using the Abyss; her spiritual form makes her petite and 'ordinary', mirroring her former legal rival Lee Mi-do. With Min's original body missing, he is framed for Se-yeon's murder, forcing the pair to live incognito. Soon after, Min instinctively revives an injured hit-and-run victim on a stormy highway, unknowingly bringing back Oh Young-cheol, the serial killer responsible for Se-yeon's death.
The investigation subsequently unearths that prosecutor Seo Ji-wook is Oh Young-cheol’s biological son (Oh Tae-jin), who stole a dead boy's identity years earlier. Ji-wook was the true mastermind behind Se-yeon's murder to prevent his identity from being exposed, and he eventually murders his own biological father to conceal his crimes. Ji-wook abducts Se-yeon and ambushes Min at an abandoned amusement park before being subdued and sentenced to death.
Because the Abyss has turned red—signaling that its life energy is exhausted—using its final charge demands the user's life. Min willingly uses the last charge to revive a mortally wounded Se-yeon and vanishes into pure light. After three years of Se-yeon mourning while continuing her legal career, cosmic entities grant Min an earthly return in recognition of his pure selflessness. Reunited, Min and Se-yeon marry, unearth their childhood time capsule, and look forward to the birth of their child.