At the end of My Date with a Vampire II, set in early 2001, Fong Tin-yau, Ma Siu-ling, and their allies succeeded in preventing the goddess Nüwa from destroying the world. Three years later, another eschatological event is about to happen.  In ancient times, Fuxi, the King of Humankind, desired to create a paradise called the "Eternal Country" in the human world. However, that brought him into conflict with his lover, the goddess Yaochi Shengmu (Holy Mother of the Shining Lake), because the latter's mission is to bring death and disease upon humankind. Fuxi eventually broke up with Yaochi Shengmu and started a new relationship with the maiden Chang'e. However, he lost Chang'e when she flew to the Moon after consuming a magic pill from Yaochi Shengmu. Fuxi blamed Yaochi Shengmu for separating him and Chang'e, and fought with his ex-lover. The Elders of the Pangu clan intervened by putting Yaochi Shengmu under custody in Heaven while Fuxi remains in the human world.  Fong Tin-yau and Ma Siu-ling are living happily in Heaven after their success in 2001. However, in 2004, Yaochi Shengmu breaks free and introduces a deadly virus to wipe out the entire Pangu clan. Fong is infected by the virus and is on the verge of dying, but he manages to transport Ma back to the human realm. Ma has to find ways to stop an imminent clash between Fuxi and Yaochi Shengmu because that could bring about the end of the world.  Upon returning to the human world, Ma travels back in time to the Song dynasty to find Fong's previous incarnation, Jim-tau (Arrowhead), and brings him back to present-day Hong Kong. At the same time, she meets her family members — her parents Ma Dai-lung and Tong Gam-bo, and her twin brother Ma Siu-fu — whom she has never seen before. She also encounters a strange girl called Fong Tin-ngai, who turns out to be her daughter from the future. She is eventually reunited with Fong Tin-yau again.  Just as relations between Fuxi and Yaochi Shengmu start to improve, and the situation becomes more stable, Fong Tin-yau, Ma Siu-ling, and their allies are confronted by Destiny, the entity that controls and dictates the fates of all beings in the universe. They need to overcome Destiny in order to change the fate of the world.