The Secret Adversary is the second published detective fiction novel by Agatha Christie, first published in January 1922 in the United Kingdom by The Bodley Head and in the United States by Dodd, Mead and Company later in that same year. The UK edition retailed at seven shillings and sixpence (7/6) and the US edition at $1.75. Reviews were generally positive on this adventure, which manages to keep the identity of the arch-criminal secret to the very end.