Silent film actress and flapper icon Louise Brooks should have been the star of this drama, which captures the launch of her career in jazz-age New York. Instead, the movie hews to a 2012 novel by Laura Moriarty that focuses less on bubbly, 16-year-old Brooks (Haley Lu Richardson) flourishing at a modern dance school in Manhattan than on the timorous, middle-aged chaperone (Elizabeth McGovern) who accompanies her from Kansas. The woman has other reasons for leaving their hometown, but hokey flashbacks and laborious conversations about her issues reveal her story to be half as interesting as her ward’s. Written by Downton Abbey showrunner Julian Fellowes and distributed by PBS, the film has a sedate TV-movie quality, unbefitting of the roaring era and its It Girl. Brooks, given second billing here, deserves her own biopic.