Sherlock Holmes is often oversimplified as a secular modern professional, with a remorselessly scientific outlook. This hypothesis overlooks late-nineteenth-century English society’s pursuit of new social possibilities for spiritualism, following challenges from Darwinist biological determinism to orthodox biblical mythology and morality. If we see Holmes in a default empirical scientism affiliated to imperial ideologies, we will remain blind to the effects of multiple countercultural and spiritual tones that also underpin the “science of deduction.” Holmes’ methods were subliminally informed by theosophy, as Doyle gleaned much of his spiritual knowledge from first- or second-hand readings on Blavatsky. Thus, Vedantic and Buddhist philosophy find inadvertent—but not coincidental—traces in Holmes through theosophy. An intellectual offspring of the trinity of Darwin, Huxley, and Tyndall, Holmes was also a child of Blavatsky’s occult philosophy. Adopting a decolonial praxis, this paper argues that comparisons between the materialistic principles of Darwin, Huxley, and Tyndall, on the one hand, and Holmes on the other, are as useful as comparing the detective’s work to Blavatsky’s theosophy.