The article examines Dickens’s last novel in the context of British imperialism, contraband opium trade in nineteenth-century China under the armed protection of the British government, and the Opium Wars (1839–1842 and 1856–1860). Although Dickens has often been discussed as one of the authors who approved of his country’s imperial domination, his last novel foregrounds a critique of colonial practices. The atavistic character of imperialism takes its moral and psychological toll not merely somewhere in the dominions, colonies, protectorates, and other territories but also ‘at home’ on the domestic ground. In The Mystery of Edwin Drood London has the face of a dingy and dark opium den or the ominous headquarters of the Heaven of Philanthropy with the professing philanthropists in suits of black. Moreover, the article seeks to discuss deep-rooted evil and darkness associated in the novel with an ecclesiastical town in connection with Protestant missionaries’ close collaboration with opium traders in the Celestial Empire. Portraying John Jasper’s moral degradation enhanced by the drug and the corruption of the ecclesiastical town, Dickens gothicises opium, and by implication, opium trade pointing to its double-edged sword effect: sullying and debasing both the addict and the trafficker. The symbolic darkness of the opium den and the churchly Cloisterham reflects the inherent evil latent in any unbridled colonial expansion and Dickens’s anti-colonial purpose.