When Captain Nigel “Gunga” Deane returns from India, he discovers that his brother has been murdered. Determined to uncover the truth, Gunga sets out on a dangerous personal campaign against the criminals responsible.

But this is no ordinary investigation. As he moves deeper into a shadowy world of organized crime, deception, and deadly revenge, Gunga becomes the unknown quantity his enemies cannot predict.

The Unknown Quantity is a fast-paced British mystery thriller by W. E. Johns, filled with suspense, danger, secret identities, murder, and relentless pursuit. Best known for his aviation and adventure fiction, Johns brings the same sense of action and momentum to this gripping crime novel.

For readers who enjoy vintage British thrillers, classic mysteries, crime adventures, and atmospheric twentieth-century suspense, The Unknown Quantity delivers a compelling journey into a world where courage and cunning can mean the difference between life and death.