A new stranger has arrived in town, to help treat opium addicts during the Ching Dynasty. But he also has been secretly conducting unorthodox tests on patients in his fancy clinic, shaping them into strong warriors with elevated strength and creeping madness. One of them escapes and crashes into Master Wong Fei-Hung's school, setting Wong off on an investigation. Meanwhile, the youthful Auntie 13 has returned from overseas and complicates things with her Westernized style and attitude, and is about to join the new clinic as major staff. To add another level of intrigue is the friendly kung fu master specializing in the Northern style, who has been affected by the serum, unleashing a powerful potential opponent for Wong!