With whom does Simon come in contact? What does Simon do for him?

Simon finds the dead pilot hanging from a tree. He cuts down the lines of the parachute to let the pilot rest in peace. 

Simon comes in contact with the dead parachutist who is, he realizes, what the boys have misidentified as the Lord of the Flies.  He tries to let the boys know of their mistake; in their frenzy around the fire, they do not realize who he is and ultimately kill him.