The Old Marquis seethed with anger, yet he lacked the courage to investigate the truth at that time. He was deeply worried that his main wife had indeed been poisoned to death by her equal life. If that were the case, he couldn't find the courage to admit his earlier mistake.
A tree needs its bark, and a man needs his face. When his eldest son had left years ago, he hadn't initially displayed any guilt. His emotions were dominated by anger. He told everyone that he hadn't done anything wrong, vowing that his main wife could never commit such an act. He insisted that his sole error was in failing to raise his son properly.