Ethel Lina White's *Step in the Dark* is a finely controlled work of psychological crime fiction, combining the apparatus of the traditional mystery with the unease of domestic Gothic. Its suspense arises not merely from the question of who is culpable, but from the instability of perception: familiar spaces become threatening, appearances conceal motive, and ordinary social relations acquire a sinister undertone. White's economical prose, atmospheric settings, and gradual disclosure of information place the novel within the interwar tradition of British sensation fiction, while its emphasis on vulnerability and psychological pressure gives it a distinctly modern intensity. White (1876–1944), a Welsh author who worked for many years in the British civil service before devoting herself fully to writing, brought to her fiction a sharp understanding of institutions, social conventions, and the dangers concealed beneath respectable surfaces. Her major novels, including *Some Must Watch* and *The Wheel Spins*, demonstrate a sustained interest in isolated protagonists—especially women—whose intelligence must contend with disbelief, coercion, or menace. *Step in the Dark* reflects this larger artistic concern with the precarious boundary between security and terror. This unabridged edition is particularly suited to readers interested in the development of psychological suspense and the literary history of crime fiction. It will appeal to admirers of atmospheric mysteries, unreliable appearances, and tightly managed tension, while also rewarding scholarly readers attentive to White's treatment of gender, fear, and social power. The novel remains a compelling example of how a seemingly conventional mystery can become an unsettling study of consciousness.