for Blue Flame by K.M. Grant
Many years have passed since the Occitanian knights fought a courageous battle to keep the Blue Flame - sparked at Christ's cricifixion and kept burning for centuries - from falling into the wrong hands. Parsifal, young son of the knight Bernard, escaped with the flame and has continued the mission to find its true keeper. His path intertwines with Raimon, son of a Cathar weaver, and Yolanda, daughter of the Catholic Count, who are falling in love. But the righteous crusades begin, setting boy against girl, family against family, neighbour against neighbour, the south against the north. The tumult rises to a roaring peak when the Inquisitors arrive to slaughter the heretics and possess the Blue Flame.
Publisher description retrieved from Google Books.