August 1923.

All is quiet in the Holmes household in Sussex as Mary Russell works on academic research while Sherlock Holmes conducts malodorous chemistry experiments. But the peace quickly disappears as out of the past comes Dorothy Ruskin, an amateur archeologist from the Holy Land, who brings the couple a lovely inlaid box with a tattered roll of stained papyrus inside. The evening following their meeting, Miss Ruskin dies in a traffic accident that Holmes and Mary soon prove was murder.

But what was the motivation? Was it the little inlaid box holding the manuscript? Or the woman's involvement in the volatile politics of the Holy Land? Or could it have been the scroll itself, a deeply troubling letter that seems to have been written by Mary Magdalene and that contains a biblical bombshell...