It is 1884, and when a fellow landlady finds her lodger poisoned, Mrs. Hudson turns to Sherlock Holmes.

The police suspect the landlady of murder, but Mrs. Hudson insists that her friend is innocent. Upon investigating, the companions discover that the lodger, a civil servant recently returned from India, was living in almost complete seclusion, and that his last act was to scrawl a mysterious message on a scrap of paper.

The riddles pile up as aged big game hunter Allan Quatermain is spotted at the scene of the crime when Holmes and Watson investigate. The famous man of mind and the legendary man of action will make an unlikely team in a case of corruption, revenge, and what can only be described as magic …