The very beginning of the story Srg. Morris comes to the Whites house with a magical monkey paw. He says the paw can grant them any wish. Mrs. White wants nothing to do with the paw but Mr. White is interested. He decides he wants to try out the paw.
Mr. White's first wish with the paw is for his house debt to go away. So he wishes for 300 pounds, which is the debt they owe. So fate decides that if he wishes for the 300 pounds, the price for that will be their son, Herbert. Herbert dies in a freak accident at work.
A week passes and the Whites haven't been the same since the incident. Mrs.White suddenly wakes up one night and thinks of a great idea. She wishes for their son to come back to life. She thought that he would come back the same. When she wishes for their son to come back, he knocks at the door.
Mr. White thought that was a bad idea. He said the only way he would be able to recognize his son is by his clothes. So when his son comes knocking at the door, he uses the third and final wish to wish his son away. He didn't want to see him all scared and scratched.
When all of this is said and done Herbert is set back to the grave. Mr.White is seen laying dead at the grave stone. A week later, Mrs.White dies too, of what we thing is a broken heart. The family is broken up and killed by the magical monkey paw.
A superstition to me is doing something over and over again if I think it is working. When I play baseball, I do the sign of the cross before I go up to bat as a sign of good luck.