"The Secret Adversary" by Agatha Christie is a detective novel published in January 1922. Two unemployed young friends, Tommy and Tuppence, form a business seeking adventure and quickly find themselves entangled in a dangerous conspiracy involving a missing woman, a secret treaty from the Lusitania, and a mysterious criminal mastermind known only as "Mr. Brown." Their investigation leads them through deception, kidnapping, and betrayal as they race to recover the treaty before it destabilizes the British government. (This is an automatically generated summary.)