In the late 21st century, a subculture of humans have emerged who have been modified genetically by a vampire-like disease, giving them enhanced speed, incredible stamina and acute intelligence. As they are set apart from "normal" and "healthy" humans, the world is pushed to the brink of worldwide civil war aimed at the destruction of the "diseased" population. In the middle of this crossed-fire is - an infected woman - Ultraviolet, who finds herself protecting a nine-year-old boy who has been marked for death by the human government as he is believed to be a threat to humans.

Eason Chan is K.C, Chan and Y.T. Lee is Aaron Kwok, both are very smart cop, who both were assign to interpol. The only thing that make them different is woman. K.C Chan is known for courting with a lot of woman and Y.T. Lee get nervous around woman. The case for this movie is about a international thief who come to Hong Kong to steal, a diamond necklace worth over 10 million US. Anyway, Yumiko Cheng who is engage with a fertilizer mogul, soon for in love with KC Chan.