Wesley (Andy Lau) is responsible for handling all the incidents that relate to extraterrestrial life on Earth (anyone remember the film "2002"?). One day, Wesley meets Fong (Rosamund Kwan) when he is looking at a blue human bone in an antique shop. Fong is an alien from the Blue Blood Planet, she left her home 600 years ago to look for the Blue Blood Bible. When Wesley tries to help Fong in her search, the Double-X Unit lead by Wai (Roy Cheung) and So (Shu Qi) is ordered to take over the case. At the same time, Kill (Mark Cheung) and Rope (Almen Wong) arrive on Earth from Blue Blood Planet, aiming to take Fong back home...