In the third Harry Potter movie based on J. K. Rowling’s wondrous series of children’s novels, filmmaker Alfonso Cuarón takes the wheel from Chris Columbus, who steered both of the earlier pictures. It would be hard to think of a director with finer credentials for the job. In A Little Princess, he brought a witty, complex understanding of the ways children instinctually subvert adult authority. His scandalously overlooked Great Expectations, updated and set in the Gulf Coast and Manhattan, preserved Dickens’s spirit, and its saturated, expressionistic images hinted at what a young Bernardo Bertolucci might have brought to a contemporary American setting. Returning to his native Mexico with Y Tu Mamá También, Cuarón articulated both the hedonism and the private terrors of a pair of adolescents on an erotic adventure that drops them without warning on the thorny path to manhood.