Will Parker lives in an enslaved world. Long ago, the Tripods - huge, three-legged machines - descended upon Earth and took control. People no longer understand automation nor machines, and unquestioningly accept the Tripods' power.
But for a time in each person's life - in childhood, before the "Capping" ceremony that stops him from questioning - he is not a slave. And Will hasn't yet been Capped. He still has time to escape.