There's a runaway train full of toxic, explosive chemicals hurtling toward an American city. Fortunately, Denzel Washington and Chris Pine are in position to stop it.
That's really about it for the plot of the movie; oddly enough, it's based on an actual event (and some of the weirder ideas in the movie actually happened in real life!)
It's a good "working the problem" movie, in the vein of Apollo 13, in which rather than fighting a living villain, the heroes confront a difficult and dangerous situation. Denzel Washington is, as always, good. It's fairly sleek, clocking in at about 100 minutes in length, and a good way to spend part of an evening.