Five hundred years ago, imperial guard Kevin Cheng was ordered to exterminate the vampires. He encountered a rare severe thunderstorm and accidentally became immortal. Ever since then, he made it his personal mission to kill vampires. He travels the world and changes his identity every twenty years to conceal his secret. He has an encounter with forensic pathologist Kay Tse in the Netherlands. Although it was only a brief encounter, Kay develops a deep admiration towards him. Kevin's pursuit of the vampire Joel Chan brings him back to Hong Kong, where he discovers that Kay and Joel have an inextricable relationship. Kevin takes on the identity of a late-night restaurant owner and interacts with different customers every night in a bid to find new clues. In the process, he meets Kay's sister (Grace Chan), who resembles his wife from four hundred years ago, as well as Grace's university classmates, Anjaylia Chan and Winki Lai. He also teaches Wong Yau-nam and Luk Wing-kuen to be chivalrous. Kay gradually begins to notice abnormalities with her body. It turns out that an unbelievable secret is hidden within her. With the help of Kevin, she is finally able to return to a normal life, until the appearance of another immortal (Eddie Kwan). For his own selfish reasons, Eddie is determined to capture Kay. Meanwhile, Joel's vampire army is conducting activities in the dark. Being at the centre of the storm, Kevin, Kay and the others cannot avoid getting caught up in the several hundred years old war between vampires and immortals...