THIS THOUGHTFUL, RAVISHING period film treats us to a work of serious historical scholarship and theoretical speculation on narrative and history, disguised as the old-fashioned plot about the difficulties leading up to a famous theatrical production. Taking as its focus the well-chosen moment in the creative conflict between Gilbert and Sullivan that was eventually resolved in their successful 1885 production of The Mikado, Topsy-Turvy seems throughout its stately first half to be leading us chronologically toward that resolution as if toward its own fulfillment. But meanwhile, in the film’s antic second half, a serious play sets in for the duration, and that traditional momentum is disrupted. By the time of the film’s complex closure — which is both bittersweet and deliberately, astutely, provocatively unsettling — resolution has broken down into multiple divisions once again: between the characteristically divergent responses of Gilbert and Sullivan to their mutual success; between men and women on and off the stage; between theatrical illusion and life behind the scenes. In the fragments from the film’s production of The Mikado — one, in particular, at the very end of the film — we rest for a while in the humor and beauty of its otherworldly charm, but with the uneasy sense of how tenuous, how arduously produced this beauty must be. This play-within-a-film is, among its many other virtues, the best present-day representation of a Gilbert and Sullivan production that I have ever seen.