"The Tripods" is a science fiction series written by John Christopher, set in a post-apocalyptic world where humanity is controlled by alien machines known as the Tripods. These towering, three-legged machines suppress human freedom and enforce a system where people are capped at a young age to maintain obedience. The story follows a young boy named Will Parker as he embarks on a journey to escape the oppressive rule of the Tripods. Along with his friends, he seeks to discover the truth about the Tripods and find a way to resist their control, ultimately striving for freedom and self-determination.