While he is on a cruise ship, the math whizz Wu Yu (Jin Han) meets a woman named Tan Jiao (Li Yi Tong), who writes web-based mystery novels. They hit it off and begin to develop romantic feelings for each other. But after the journey is over, they both suffer differing amounts of memory loss. Wu Yu's life is also turned upside down when his sister is killed and his mother dies shortly after. The two meet again by chance after many months apart, but things have changed for both of them. Wu Yu has become an auto mechanic who spends his time in melancholy - and trying to get to the bottom of what happened to his family. Tan Jiao does not immediately recognize him, but still feels the pull of attraction toward Wu Yu. But as they try to work out what happened to their memories - and search for the person who killed Wu Yu's sister, they begin to wonder if something very strange happened on the cruise ship.