“Lamb to the Slaughter” has several themes, but perhaps the most prominent and compelling is jealousy or, more precisely, the speed and intensity with which love can turn to hatred. Mary Maloney idolizes her husband. When he comes home, she waits on him devotedly and feels a sense of bliss merely because he is close to her:
She loved to luxuriate in the presence of this man, and to feel-almost as a sunbather feels the sun-that warm male glow that came out of him to her when they were alone together.
When he tells her that he has decided to leave, however, Mary first experiences a sudden numbness. She feels nothing at all except a slight nausea. Then, equally suddenly, she walks up behind him and smashes a frozen leg of lamb as hard as she can against the back of his head. Her feelings as she does this are not described, and she does not seem to think about it until after she has done it. It is an automatic animal reaction of fury and jealousy at the knowledge that she is about to lose her husband to another woman.
After the murder, Mary becomes cool and logical. All the sentimentality has drained out of her. Love died with her husband’s betrayal, but jealousy, at least, has been satisfied.