Damon Blackthorne, a cold Dark Immortal who has lived for three hundred years, has never let his heart be stirred. Until a rogue Demon Ring chooses an ordinary girl, Sophie. Her pure soul instantly claims the ring, putting his existence on the line. To retrieve the ring and sustain his life, Damon signs a fake marriage pact with Sophie: he shields her from her cruel family, and she keeps the ring for him. As they stay side by side, the hardened immortal learns what it means to protect someone for the first time, while the wounded girl finally receives tender care. When the solar eclipse arrives, the truth unfolds: if the immortal survives, the ring bearer will fade away. Will he uphold the pact and regain his power, or give up eternal life for love?
