British author Jecks displays an impressive command of period in his ponderous 24th Knights Templar mystery (after 2007's Dispensation of Death). In 1325, Sir Baldwin de Furnshill, a Knight Templar, and his friend Simon Puttock accompany Queen Isabella of England on a diplomatic mission to her brother, France's Charles IV. Soon after the queen and her entourage arrive in France, the Comte de Foix, ""a powerful magnate,"" is found stabbed to death with Sir Baldwin's dagger. Accused of murder, Sir Baldwin must once again turn sleuth to clear his name-and save the queen's mission. A lengthy list of characters at book's start will be welcome to many readers, who may have trouble keeping them straight. A glossary of archaic words like ""calefactory"" and ""tabor"" is also useful.