O Jerusalem is the fifth book in the Mary Russell series by Laurie R. King. Set during the voyage of Mary Russell and Sherlock Holmes to the Holy Land, the action of this novel takes place chronologically during the action of The Beekeeper's Apprentice. In Palestine Mary and Sherlock meet up with Mahmoud and Ali Hazr, two apparently Bedouin guides, to counter a plot against the British in Jerusalem under General Edmund Allenby. Source: Wikipedia (en)