This paper recalls the early life of Dr Arthur Conan Doyle when his writing centred briefly on India. The significance of a young female skeleton given to the museum of the Royal College of Surgeons of Edinburgh in 1879 is reviewed. Morphometric and genetic evidence is provided to show that the skeleton originated in the Andaman Islands. It is suggested that Doyle saw it during his undergraduate or early postgraduate years, leading him to introduce an Andaman Islander into his novel The Sign of the Four, published in 1890. Like his inspiring predecessor Walter Scott, Doyle wrote of India but did not visit the country: both authors learned indirectly of the Indian Raj and the Indian Medical Service. Doyle knew of the convict colony established after the Sepoy Mutiny of 1857 at Port Blair, capital of the Andamans, but the reason he chose an Islander to commit murder in London has, until now, remained contentious.