Bayard's Granny dies. She is killed by a man named Grumby, having been "set up" by Ab Snopes. Bayard learns, regretfully, that he possessed the power to shape events but did not exercise that power. He reflects on this in a moment where he places himself ahead of the narrative action and looks back retrospectively.
This moment in the novel, using the dramtic irony of direct foreshadowing of Granny's death, allows Bayard to recognize his own role in the event. He could have stopped Granny from getting out of the carriage and going into the trap, but he did not.
"We tried. I keep on saying that because I know now that I didn't. I could have held her, turned the wagon, driven away, holding her in it."
The lesson Bayard takes away from this episode is complex. He sees that there was a moment when action was called for and he also sees that one must recognize that moment for what it is because, once it has passed, no amount of effort can make a difference.
In this way, Bayard learns that responsibility is not only defined in the abstract and in fulfulling ones duty by doing chores, etc., but is also defined by enacting one's inter-personal duty when the moment calls for action.