Guilt is an ongoing theme throughout the novel Crow Lake. How did this feeling affect the children’s relationships and the choices they made immediately following the death of their parents? How did it affect their adult lives? Who would you say was most stricken with this feeling?

Following the death of their parents, Matt, Luke, Kate, and Bo's life plans are up in the air. Initially, their aunt proposes that Matt work on the family farm, Luke go to college with the remainder of the family's savings, and Bo and Kate live with an aunt and uncle in another city. Luke and the other children reject this plan, in part because Luke refuses to go to college while Matt stays home, suggesting a sense of guilt at the prospect of having opportunities his brother is denied.
The children face hard times but get through them together. Eventually Kate goes to college and becomes a successful zoologist while Matt stays home and eventually suffers an accident.
Kate is clearly racked by guilt, and it nearly ruins her relationship with Matt and with her partner Daniel. Eventually, Matt's partner Marie confronts her, saying that the only person who feels regret about how things played out is Kate.
This suggests a lesson, that Luke's guilt dissipated because he made an intentional decision to stay home from college while Kate's guilt stayed with her because she took advantage of an opportunity her brothers turned down and felt conflicted about this. The book doesn't suggest that this was a bad decision, necessarily, but it's clearly one that Kate had not fully made peace with. Marie's confrontation also suggests that Kate's feelings of pity and guilt about Matt's accident are unhelpful. Matt had made peace with his life and was content, and Kate's guilt was not rooted in Matt actually being wronged, but in her own projections onto Matt's life.