Kimball O'Hara, the "Kim" of the famous Rudyard Kipling novel, has disappeared. Fearing a geopolitical crisis in the making, Mycroft Holmes sends his brother and Mary to India to uncover what happened. En route, they encounter the insufferable Tom Goodheart—a wealthy young American who has embraced Communism—traveling with his mother and sister to visit his maharaja friend, Jumalpandra ("Jimmy"), an impossibly rich and charming ruler of the (fictional) Indian state of Khanpur. With some local intelligence supplied by Geoffrey Nesbit, an English agent taught by Kim, and accompanied by Bindra, a resourceful orphan, the couple travel incognito as native magicians. Ultimately, their journey intersects with the paths of the Goodhearts, Jimmy, and the enigmatic Kim.