Gage is the son of Dr. Louis Creed and Rachel Creed and younger brother of Ellen Creed. His family moves to the country side, and right next to their new house is a road where trucks pass by many times a day. Nearby their house is also a pet cemetery built by children of the neighbourhood, for many pets have been killed on the busy road during the years.
Soon after the family settles in to their new home, they have a picnic on the field between their house and that road. The 2-years old Gage is flying a kite, but loses his grip and the kite gets away. During the few moments that the boy remains unsupervised, he starts following the kite to the road. Unfortunately, at this time a high-speeding truck is heading towards the spot. His father, Louis, tries to catch the baby but fails. In the middle of the road Gage picks up the string roll of the kite, does not understand what's going on, and gets hit by the truck.
After Gage's funeral he's laied to rest normally, but Louis knows about another cemetery beyond the children's pet cemetery; an old indian burial ground that has the power to bring the dead back to life. He's warned, multiple times, not to bury a person up there because the person you put up there is not the person that comes back, for the ground has gone sour. Grief-stricken, the father buries his baby there anyway, in hopes that it would be alright as he did it so soon after the death.
A wendigo, a spiritual creature that the indians believed could touch you and turn you into a cannibal, takes over Gage's body and returns to his family. It manages to kill two people before Louis finds out that "his son" has come back. Immediately the father also learns that Gage came back wrong, and decides to put him back to sleep. In essence, Gage never came back from the dead but only the wendigo in his body. The wendigo pretends to be him, gets constantly called Gage and the father keeps seeing it as his son.
Gage is a fictional character created by Stephen King, but King based the story on true events from his own life; King once lived in a house with a pet cemetery and a busy road nearby, and his son got nearly run over on that road.