Donnelly (played by Brendan Gleeson) is experiencing a difficult time. Following his wife's passing, he's on the train heading home when he encounters a young boy (Rúaidhri Conroy) who isn't shy about speaking his mind—what my grandmother would have called exceptionally unusual. The boy directs his remarks toward a couple who join the train later and seem visibly upset. It becomes clear that the woman (Aisling O’Sullivan) and her husband (David Wilmot) are dealing with their own distressing circumstances, and the boy's sharp comments quickly contribute to the first of several unfortunate incidents during the journey. This experience gives Donnelly something to consider, both on the train and later when he returns home to his rabbit named David. If you’re struggling with grief, this film might not be ideal, but otherwise it offers a darkly humorous perspective on human nature. There are moments where it feels like it's challenging viewers to laugh, fully aware that there's little genuinely amusing about the situations unfolding. Conroy is remarkably naturalistic in his performance, and Gleeson provides excellent contrast as he grapples with what has happened. It does occasionally amplify events for dramatic impact, but I believe this is part of what makes it entertaining and deserving of a viewing. This represents Celtic humor at its most somber.

Source on TMDB