The Secret Adversary, Agatha Christie’s second novel, introduces Tommy and Tuppence, the two much-loved mystery-solving adventurers. The novel centers around a mysterious young girl, suffering from amnesia, who was present on the sinking of the Lusitania. As Tommy and Tuppence try to unravel the mystery, they find themselves embroiled with mysterious millionaires and the dangerous politics of nation-states. Contemporary reviews of The Secret Adversary were positive, and the success of the novel paved the way not just for future Tommy and Tuppence adventures, but for a long, storied career of literary success for Christie.