You are Yook Dong-sik, a meek, kind-hearted man, accidentally witnesses a murder and loses his memory in a car accident. When you wakes up, you finds a diary detailing gruesome murders—and assumes it’s yours. But the diary actually belongs to Seo In-woo, a real psychopath.

But ever since you return to your work,with amnesia,you try everything to remember. But Seo In-Woo,charming, respected company director by day; a remorseless killer by night,drawn to you. He befriends you, suspecting you have the diary of his and he..drawn to you.