Casey Hoult had a fatal accident. But instead, she woke up in a very different state. She realized that her soul had been trapped in the body of a woman named Clara who had died after the wedding, allegedly due to poisoning. Casey, who didn't know what to do, was finally met by a mysterious man who couldn't be seen by others. He promised to always accompany her for 99 days as Clara. Within 99 days, Casey had the opportunity to uncover the facts of the accident that happened to her and reveal who had poisoned Clara. During those 99 days, Casey lived as Clara, which forced her to act as the wife of Nathanael William Rudolf, a noble man who inherited his royal family's company and loved Clara very much. Slowly, Casey felt comfortable living with Nathan, but she didn't know what would happen if Nathan found out about who she really was. She also didn't know if she would still be alive after 99 days. These facts caused her mental agony, and the truth about the people closest to her, including her lover, made her very sad. What happened to Casey and the people around her? Would she be immortal in Clara's body with the help of the mysterious man? Or would she return to her original body still in a coma? Or maybe she would die and not have a chance to live with Nathan? Let's read on because this story is not only about crime but also about love after marriage.