Nestled in the Himalayas, Tibet was a forbidden land in the 19th century. But imperial interest tempted the British to send spies dressed up as Buddhist monks. In 1879 they sent a young Bengali schoolmaster. At around the same time, an illiterate Lepcha tailor from Darjeeling was going in search of a mysterious river across the deepest gorge on earth. History has not remembered them. Reports of their adventures have rotted away in dusty government archives. From an antique bookshop at Shimla to the forests of Shingalila, from the old graveyard in Kolkata’s Park Street to a remote Arunachal village, the author has pieced together an incredible narrative.