The Monkey's Paw is a legendary item of evil intent that allowed whoever held it to obtain wishes, at a horrific price - being prone to twist the wishes in order to unleash the worst outcomes.
The premise is simple: whoever picks up the paw has the knowledge that he can ask and get granted one wish per finger that remains standing in the paw. However, although the wish is indeed granted, it comes true under very terrible circumstances and the outcome is hardly worth the price. This happens through the terrible circumstances that occur when someone messes with fate, giving the "lesson" that the user should accept his life as it is, and interfering with destiny may be even worse.
The object appears for the first time in W. W. Jacobs' short horror story The Monkey's Paw, (1902), in which a family comes across a gift given to them by a fakir, who cast a spell on a mummified monkey paw so that it could grant wishes. Although one of the main characters discourages the rest to use the hand, they still do, which brings terrible consequences.
The item has since entered mass media as one of the most famous examples of a "cursed item" in fiction, with many variants found across multiple media, like videogames, movies, series and many other references. For instance, the cursed paw appears as the main plot item in one of the "Treehouse of Horror" short episodes in the TV series The Simpsons.
The short story involves Mr. and Mrs. White and their adult son, Herbert. Sergeant-Major Morris, a friend who served with the British Army in India, introduces them to a mummified monkey's paw. An old fakir placed a spell on the paw, it would grant three wishes. The wishes are granted but always with hellish consequences as punishment for tampering with fate. Morris, having had a horrific experience using the paw, throws the monkey's paw into the fire but Mr. White retrieves it. Before leaving, Morris warns Mr. White that if he does use the paw, then it will be on his own head.
At Herbert's suggestion, Mr. White flippantly wishes for £200, which will enable him to make the final mortgage payment for his house, even though he believes he has everything he wants. The next day his son Herbert leaves for work at a local factory. Later that day, word comes to the White home that Herbert has been killed in a terrible machinery accident. Although the employer denies responsibility for the incident, the firm has decided to make a goodwill payment to the family of the deceased. The payment, of £200, exactly matches the amount Herbert suggested his father should wish for.
10 days after their son's death and a week after the funeral, Mrs. White, almost mad with grief, asks her husband to use the paw to wish Herbert back to life. Reluctantly, he does so. Shortly afterward there is a knock at the door. As Mrs. White fumbles at the locks in an attempt to open the door, Mr. White, who had to identify his son's mutilated body, and who knows the corpse has been buried for more than a week, realizes that the thing outside is not the son he knew and loved, and makes his third wish.
The knocking suddenly stops. Mrs. White opens the door to find no one is there.