Natalie Babbitt foreshadowed many things about the man in the yellow suit.

For example, she made him look like an extremely selfish and controlling person when he turned in Winnie in to her parents so he could get the Fountain of Youth so he could live forever and take over the world in some way.

Also the way that it showed that he had control because he was the only one that knew where Winnie was. Her parents obviously had to sell the wood to get Winnie back because she means more to them than the wood.

Foreshadowing

Tuck Everlasting