There is a void in the relationship as the story opens. From all accounts, Mary is a dutiful wife. She tends to her husband's needs and does not display any signs that she is a bad wife or someone who is unresponsive to her husband. Mary sits silently while he tells her that he is leaving her. The true intent of her husband's words can be seen in the follow up line to the breakup:
"So there it is," he added. "And I know it's kind of a bad time to be telling you, bet there simply wasn't any other way. Of course I'll give you money and see you're looked after. But there needn't really be any fuss. I hope not anyway. It wouldn't be very good for my job."
The emotionally blunt manner in which he speaks to her indicates much about the level of fault in their relationship. Certainly, she is not justified in beating him to death with a leg of lamb. Yet, he does not really display much in way of sensitivity to her as he ends their marriage. He speaks of how he hopes there would not be "any fuss." He reflects on how this "wouldn't be very good for my job." Even when she leaves to cook the fateful dinner, he yells that he is not going to be staying in that evening. It is evident that he wants to leave this relationship at all costs, leaving her in a condition of loneliness. It is hard to blame him for the problems in the relationship because Mary kills him with the leg of lamb. Yet, I think that Mr. Maloney's attitude towards both the marriage and his desire to get out of it reflects how he might be more to blame for what she does to him.