Based on the same source as CLAN OF AMAZONS, with many of the same characters (played by different actors). The plot is typical Gu Long - waaaay too many characters and more twists and intrigues than Agatha Christie's entire output, but somehow I managed to follow everything that was happening and enjoyed the film a lot. The rooftop duel referred to in the title is also referenced in Stephen Chiau's FORBIDDEN CITY COP and Andrew Lau's THE DUEL - which I might have to watch again to see if it's actually a remake of DOTC. Recommended for fans of the CY/GL collaborations. The film has more comedy than other films from the duo.