The year is 1936. The discovery of correspondence from 1000 years before between Bertha of Lotharingia, Queen of the Franks, and a Caliph in Baghdad are somehow linked to 'a series of grisly disappearances from European cathedrals'. British Intelligence will again turn to Marion Bailey to head to Bertha's old haunts to investigate. Too late, though, she will come to realize that her employers, including her nemesis Jeffrey Willcox, might very much want her to fail.