1869. Tibet is closed to Europeans, an infuriating obstruction for the rapidly expanding British Empire. In response, Britain begins training Indians to undertake illicit, dangerous surveying expeditions into Tibet. Balram is one such surveyor-spy, an Indian schoolteacher who has worked for the British, often alongside his dearest friend, Gyan. But Gyan went missing on his last expedition and is rumored to be imprisoned within Tibet. Desperate to rescue his friend, Balram agrees to guide an English captain on a foolhardy mission. The captain, disguised as a monk, wants to personally chart a river that runs through southern Tibet. Their path will cross fatefully with that of another Westerner in disguise, 50-year-old Katherine. Denied a fellowship in the all-male Royal Geographical Society in London, she intends to be the first European woman to reach Lhasa.

Nine-year-old Jai drools outside sweet shops, watches too many reality police shows, and considers himself to be smarter than his friends Pari (though she gets the best grades) and Faiz (though Faiz has an actual job). When a classmate goes missing, Jai decides to use the crime-solving skills he has picked up from TV to find him. He asks Pari and Faiz to be his assistants, and together they draw up lists of people to interview and places to visit. But what begins as a game turns sinister as other children start disappearing from their neighborhood. Jai, Pari and Faiz have to confront terrified parents, an indifferent police force and rumors of soul-snatching djinns. As the disappearances edge ever closer to home, the lives of Jai and his friends will never be the same again.