Lawhead, a prolific writer of historical novels, ably captures the colorful swirl of Crusader-era Byzantium and Spain in this final installment in his latest trilogy (The Iron Lance; The Black Rood). In Constantinople on a trip to the Holy Land, where her Scottish family has battled Saracen invaders for two generations, Celtic beauty Caitríona is desolate when her father is stabbed to death in the crowded cathedral of Ayia Sophia by unscrupulous Templar Renaud de Bracineaux. Eager to seek revenge, Cait steals a letter from Renaud disclosing the whereabouts of the Holy Grail, called the Mystic Rose, and sets off in her father's ship for Spain, with the Templars in hot pursuit. Romanced on the Iberian peninsula by a handsome Moorish prince, a Valentino clone lacking only a desert and a blue lens filter, Cait finds the Grail and defeats the Templars with the help of her faithful Norse sailors and the prince's men. Otherwise conventional, this historical potboiler takes an unexpected turn at its conclusion, when Cait sips "a darkly gleaming crimson liquid" from the Grail and has a vision of a da Vinci–like "Passover Feast." Blessed in the vision by a young man named Yeshua, she emerges bearing stigmata and is charged with making a distinct career change. The action drags in places, and an unnecessary early 20th-century subplot is wrapped up after the climax, but Lawhead's robust characterizations and vivid descriptions of exotic locales should satisfy fans. (Oct. 10)