The problem that arises in “The Monkey’s Paw” is that when they make wishes on the paw, the consequences are not what they expected.
In the story, a family is having a relatively peaceful evening until they get a visitor. Mr. White hasn’t seen Sergeant-Major Morris for many years. He is grizzled and has a trinket with him. He has told stories about the Monkey’s Paw, which has had a spell put on it by an old “fakir,” a holy man.
“… He wanted to show that fate ruled people's lives, and that those who interfered with it did so to their sorrow. He put a spell on it so that three separate men could each have three wishes from it."
The Whites are interested in the power the paw has, and don’t focus on its curse. When they wish for money, their son dies. They got the money, but with an unintended consequence. When their son dies, they wish him back to life. He comes back to life, but we are to believe he came back as a grizzled monster. To save the family from their own foolishness, Mr. White makes a wish on the paw for his son to be dead again.
A macabre twist on "be careful what you wish for," this story focuses on how solutions to problems sometimes bring problems of their own. Actions have consequences, and the ends don’t always justify the means.
In the later part of the story, Mrs. White uses the monkey's paw to fulfill her second wish of bringing her dead son back to life. Mr. White realizes that their son out of the grave would not be a good sight. Thus, as Mrs. White is just about to open the door of the house in reply to her son's knocking, Mr. White uses his last wish to undo the last wish. Thus after a dramatic turn of events, the story ends on a sad note.