The White Mountains

In the novel, adolescents undergo a process called 'Capping' once they reach the age of fourteen. The giant alien machines known as Tripods attach metal meshes to their heads, effectively brainwashing them into submission. The protagonist, Will Parker, flees his village to avoid this exact fate.

The story follows a thirteen-year-old boy named Will Parker, who lives in an English village under the rule of the Tripods. As he nears his fourteenth birthday and the inevitable Capping ceremony, he becomes disillusioned with his society. He eventually joins a resistance group planning to travel to the titular White Mountains.

The White Mountains, published in 1967, is the first novel in John Christopher's celebrated Tripods trilogy. The series follows humanity's struggle against giant, alien machines that have enslaved the Earth. The subsequent books in the series are The City of Gold and Lead and The Pool of Fire.

In the novel, the Tripods are giant, towering alien machines that rule over a futuristic, dystopian Earth. They maintain control over the human population by surgically attaching metal Caps to adults once they turn fourteen. These machines are central to the conflict of the entire trilogy.