The dismaying news is that this heart-tugger by Chinese filmmaker Wu Tianming drags out one of the hoariest setups in the Big Book of Plots for Subtitled Movies that of a crusty geezer softened by the love of a cute kid. The better news is that the cute kid in The King of Masks is an impostor (Zhou Ren-ying), who clings to old Wang (Zhu Xu), a popular 1930s street performer. Wang's specialty, passed down from man to boy in his family, involves a lightning-quick change of masks. Childless, pining for a ''grandson'' to inherit his professional secrets, Wang adopts ''Doggie'' and is furious to learn that his boy is a desperate girl. (The actress was herself sent away by her parents to join an acrobatic school at the age of 3.) Of course, Doggie turns out to be quicker and more resourceful than any average boy.
The brutal sexual inequalities contrast harshly with Wu's colorful evocation of exotic pomp and ritual, including opera, fireworks, and pipe-smoking ceremonies. Throughout, sadness permeates Zhou's every move, a reminder that acrobatic flexibility means nothing to a child unloved because she doesn't have (as Wang calls it) ''a little teapot spout.'' B-