The North West Frontier, 1925. Bandits have stolen The Eye of the Storm, a legendary diamond said to give its owner control of India. A party of Bolshevik fanatics is after it and so is Prince Mahsud of Beshandu. The Oxford-educated Pathan prince believes that with the diamond in his hands he can lead a newly independent India. The only way to prevent a war is to get the diamond back and Sir Oswald Masterman of the Imperial Intelligence Service knows the right man to do it – Captain John Caspasian of the Twelfth Gurkhas. Rebellious but highly effective, Caspasian is glad to be off desk duty and back in action. With his hand-picked assistant, Gurkha Sergeant Ganga Limbu, Caspasian sets off for Beshandu disguised as the escort for a routine tribal council.