story: Stewart's dad built a treehouse for him in the back yard. Stewart and his friends had great fun with the tree house. Stewart grew older and eventually had a son of his own. There were no large trees in Stewart's back yard. Instead of a tree house, Stewart built a fort for his son.
 selected sentence: Instead of a tree house, Stewart built a fort for his son.
Stewart builds a fort for his son >Causes/Enables> Stewart's son plays in the fort