After years of ignoring his postcards, Jack visits Nicky and tells him about his family.
The entirety of the Vietnam storyline with Jack and his presumed dead brother Nicky is like a Greek tragedy.
Nicky tries to explain that what happened in Vietnam was an accident, but Jack won’t hear him out, he’s already decided to sever ties entirely.
Nicky’s addiction and PTSD, leading to him accidentally killing a kid is unfathomable, but it is the culmination of all those events that I think feels the most heartbreaking for the characters.