Mary's careful planning plays a significant role in the outcome of the story. For example, her initial decision to cover up the murder by cooking the lamb shows her thought and tactics in trying to hide the evidence. This is evident when she thinks, "If anyone came in, they would find everything normal." Secondly, Mary's calculated decision to create an alibi for herself and her husband by pretending they were going out of town demonstrates her meticulous planning. As she tells her husband, "You'll need to eat properly while I'm gone. I've made some lamb chops for you to eat cold." This shows that she was not only thinking about herself but also trying to ensure that her husband was not seen as a suspect. Finally, when the police arrive to investigate the murder, Mary's anxious behavior adds to the tension of the story. This is demonstrated when the narrator notes, "She stood up and looked at him uncertainly. He went past her into the living room and stopped short." Her behavior implies that she is hiding something, which creates a sense of unease for the reader. In conclusion, Mary's careful planning and attention to detail are crucial in influencing the outcome of the story. Her actions not only contribute to the suspense of the story but also demonstrate the extent to which she was willing to go to conceal her crime.