Psychologist Vivian is abandoned by her family. One night, a black-winged man named Killian falls from the sky, and an accidental kiss binds them by a life-and-death contract. By day, he is a lost puppy Ian; by night, he returns to his demon form. Vivian uncovers his betrayal by heaven, they fight the mastermind, and Killian gives up his divine status to stay with her.
