A new entry in the historical mystery genre, this set, in 1100, in a Jerusalem occupied by conquering Crusaders. Sir Geoffrey de Mappestone of England, a landless younger son educated in France, is a knight in the service of Lord Tancred of Italy and Tancred’s uncle Bohemond. The city is being ruled by quietly warring religious factions—Archbishop Daimbert, the Patriarch, in service of the Pope; the Benedictines of the Church of the Holy Sepulchre, headed by Duke Godfrey of Lorraine, who calls himself the Advocate; Augustinians, Cistercians, and others, all fighting for power. Both religious and soldier communities are frightened by a series of killings. The victims are three priests and two knights, one of whom, a friend of Geoffrey’s, is found dead in the house of Greek widow Melisende Mikelos—and, like the others, stabbed to death with a gaudy knife that quickly disappears. Geoffrey is commissioned by Tancred and, later, by the Advocate to investigate. This he does, at numbing, bumbling length, until a final bloody battle. Readers interested in the place and period will find them portrayed here in infinitesimal detail. Puzzle fans must contend with an endlessly repetitive, confusing, and dull slog.