Very short version (at least compared to Rand’s turgid prose): she sets up a situation where a bunch of straw-man liberal baddies (a politician, a journalist, an academic, an actor, etc. – the usual suspects with the usual sins) she thinks are against capitalism are on a train with a bunch of other men, women and children.
The diesel locomotive breaks down, but there are no spares available to replace it. The politician uses his clout to demand that the train’s journey is continued so he can make his campaign rally. Over the objections of a brave engineer, a steam locomotive is used. The train continues on its way, eventually entering a long tunnel through the Rockies. Everyone on board is asphyxiated (yes, including the innocents, and yes, including the children), and Rand makes it clear they all got what they deserved.
This is the book that GOP politicians demand their staffers read and that they hand out to promote neoliberalism. A first edition open to that chapter should be displayed in a glass case in this museum.