In the lat­est install­ment of this acclaimed series, Sher­lock Holmes’s daugh­ter faces an elab­o­rate mys­tery that threat­ens the sec­ond most pow­er­ful man in His Majesty’s gov­ern­ment. In 1918, dur­ing the height of the Great War, Joan­na Holmes and the Wat­sons receive a late-night, clan­des­tine vis­it from Sir William Rad­cliffe, the Chan­cel­lor of the Exche­quer, who brings with him an ago­niz­ing tale of black­mail, a case so sen­si­tive that it can only be spo­ken of in the con­fines of 221B Bak­er Street. An unknown indi­vid­ual has come into pos­ses­sion of sala­cious pho­tographs, which sul­ly the fam­i­ly name and may force the chan­cel­lor to vacate his seat on the War Coun­cil. The black­mail­er has in their pos­ses­sion reveal­ing pho­tographs that show Sir William’s grand­daugh­ter in roman­tic encoun­ters with a man oth­er than the aris­to­crat to whom she is engaged to mar­ry. Should the pic­tures be released to the pub­lic, the wed­ding would be imme­di­ate­ly called off, and the prospect of the grand­daugh­ter ever find­ing a suit­able hus­band would van­ish. Sir William’s fam­i­ly has been forced to pay exor­bi­tant sums for sev­er­al of the pho­tographs, but even more remain in the blackmailer’s pos­ses­sion. Scot­land Yard can­not be involved for fear of pub­lic dis­clo­sure. It thus falls on the shoul­ders of Joan­na and the Wat­sons to expose the black­mail­er and pro­cure the pho­tographs before irrepara­ble harm comes to the chan­cel­lor and his family.