The protagonist, Jack Harrison, stuck with me as this very raw, almost frustratingly stubborn guy. A freight train conductor with ghosts from the past, trying to do the right thing on a path that feels destined for disaster from page one. I found his sections less 'action hero' and more a study in quiet desperation, which really worked for me.
Sofia Vega is his perfect narrative counterpoint. As the risk analyst brought in to assess the impending chaos, her logic-driven perspective clashes with Jack's gut instincts in a way that reveals both their characters. Their dynamic, especially the way their mutual professional respect slowly morphs into something more vulnerable under pressure, was the core of the book for me.
You also can't forget the antagonist, the corporate fixer known only as Richter. What made him chilling was his bureaucratic coldness; he's not a mustache-twirling villain, but a man who sees a catastrophic event as a spreadsheeting problem. The smaller characters, like the veteran signalman Wilkins, add crucial texture. Their conversations in the signal box felt like the heart of the old world about to be shattered.