Includes a detailed biographical note and a brief history of the Lusitania.The Secret Adversary introduces Tommy Beresford and Tuppence Cowley, two young friends who form Young Adventurers Ltd. and advertise themselves as “willing to do anything. Go anywhere…no reasonable offer refused.” They were the characters Christie most enjoyed.AGATHA CHRISTIE is the world’s best-selling mystery writer. She wrote eighty crime novels and short story collections, nineteen plays, and several poetry collections. Her books have sold more than a billion copies in the English language and another billion in a hundred other languages.