Clearly everyone will have their different ideas based on this question, however, for me, the climax of the tale where it becomes clear how the story will end comes when the couple have wished for their son's return and then the sound of their "son" knocking on the door can be heard. We see hear the two differing reactions of Mr. and Mrs. White. Mrs. White is depsperate to see her son again, and can't understand her husband's reluctance, wheras Mr. White does everything he can to stop his wife from going down:
She ran to the door, but her husband was before her, and catching her by the arm, held her tightly.
"What are you going to do?" he whispered hoarsely.
"It's my boy; it's Herbert!" she cried, struggling mechanically. "I forgot it was two miles away. What are you holding me for? Let go. I must open the door."
"Don't let it in," cried the old man, trembling.
At this point it is clear that the conflict between the married couple will dictate the ending: Mrs. White will do anything to see her son again, but Mr. White, as indicated by his reference to his "son" as "it", will do anything to stop this grissly reunion - including using his last wish on the monkey's paw to banish him back to his death.