Christopher John. The White Mountains. Tripods 1

New York, London: Simon & Shuster for Young Readers, 2003.
The novel was first published in 1967.The Tripods is a series of young adult novels written by John Christopher, beginning in 1967. The first two were the basis of a science fiction TV series, produced in the United Kingdom in the 1980s.
Life goes on largely as it had in the pre-industrial era, excepting that all adult humans are subject to Tripod control. Protagonist Will, a thirteen-year-old boy living in the (fictional) English village of Wherton, is looking forward to the next "Capping Day", until a chance meeting with a mysterious Vagrant named Ozymandias prompts to discover a world beyond the Tripods' control. He is accompanied by his cousin Henry, and a French teenager named Jean-Paul, nicknamed "Beanpole". The novel climaxes with Henry and Beanpole discovering that earlier, unbeknownst to them, Will was captured by a Tripod and implanted with a tracking device, intending to expose the human resistance. When Henry and Beanpole remove the device, a nearby Tripod attacks them; but the boys defeat the Tripod and eventually join the resistance, located in the titular White Mountains (most likely the French Alps).