At the close of the year 1918, forced to flee England, Sherlock Holmes and his nineteen-year-old apprentice Mary Russell enter British-occupied Palestine under the auspices of Holmes's enigmatic brother, Mycroft.

Amid the exotic bazaars and verminous hovels, they encounter a rash of unsolved murders and an adversary whose lust for power could ignite a tinderbox of hostilities just waiting for a spark...