The climax of the plot is the turning point of the story, in which the action or outcome has not yet been decided and could go either way. In "The Monkey's Paw," the climax occurs at the very end of the story when Mr. and Mrs. White hear the knock on the door after Mrs. White has wished that Herbert would return to their family. The scene is incredibly tense, with Mrs. White scrabbling at the door to open it to her beloved son, while Mr. White fears the worst sort of abomination may enter their home. This moment is the climax, because the reader does not yet know the outcome of the story--it is still undecided whether or not a disfigured Herbert will creep into the house and kill them all or if Mr. White will find a way to stop him. The falling action and resolution occur as Mr. White makes his final wish and the door opens to an empty street. The reader immediately can relax--no disfigured zombie-Herberts make an appearance-- and the story ends peacefully enough.
As was mentioned in the previous post, the climax of a story is the moment in the plot where tension reaches its highest point. Although it could be argued that the climax of "The Monkey's Paw" comes at the end of the story when Mr. and Mrs. White hear the knocking at their door, I would consider the climax to come earlier in the plot. In my opinion, the climax of the story takes place when Mr. and Mrs. White hear the news of Herbert's accidental death and find out that their family will receive two hundred pounds in compensation. Surprisingly, two hundred pounds is the exact amount of money Mr. White wished for. At this moment in the story, the characters and audience realize that the monkey's paw is truly supernatural and nefarious. The characters and audience also understand that the next two wishes will come with negative consequences. The tension in the story immediately rises after the Whites find about their son's death and the amount of money that they will receive in compensation.