The kid was a robot that Robert Ford (Anthony Hopkins) had made of himself last season. He remade his entire family as hosts/robots. Before he died in the finale last season, it appears that he put a message in the boy's head for Man in Black/William. The message he was saying is basically that Man in Black found the center of Arnold's maze, but that game wasn't for him, and he knew he was sad about that, so he decided to make a real game that actually was meant for him. Man in Black is happy because the stakes are real now, and he can actually die in the park. Ford is saying basically that Man in Black doesn't have to keep doing the same adventures with just higher stakes, but that there actually is a game going on now that he's mean to play.
he said, ""now, you're in my game. And in this game, you have to make it back out [of the Maze], you have to find the door. Congratulations, William, this game is for you. The game begins where you end, ends where you began...Everything is code here William, you know that more than anyone""