If you have never read Ayn Rand's legendary 1957 novel, ''Atlas Shrugged,'' (guilty!) or seen the 2011 dystopian fantasy ''Atlas Shrugged: Part I'' (not guilty, alas), you may have trouble parsing who's doing what and why in that movie's narratively addled sequel. ''Atlas Shrugged: Part II,'' which opened on Friday and was not shown in advance to critics for The New York Times, takes off where ''Part I'' left off. Like the first, it opens in 2016 with the world gripped in an economic crisis (and rife with amusingly torpid Occupy-style protests) that has led to an astonishing development that sounds like an environmentalist's dream: because gas costs more than $40 a gallon, Americans now rely on railroads as their major means of transportation.

How the infrastructure materialized on a large enough scale to support the nation's newly train-hopping citizens isn't addressed in the first movie, nor is it taken up in ''Part II.'' No matter, business is brisk...