The first in a series of medieval mysteries by an author well known for her historical novels (When Christ and His Saints Slept, 1995, etc.) introduces 20ish Justin de Quincy, a foundling who's just discovered that his father is the Bishop of Chester. The Bishop, in the guise of charity, has overseen Justin's education and insured his welfare, but he refuses to acknowledge their relationship. Stunned and furious, Justin flees. On the road to London he comes across a pair of cutthroats and the Winchester goldsmith they've left to die--Gervase Fitz Randolph, who begs Justin to deliver a letter, hidden on his person, to Queen Eleanor in London. All England is talking about the disappearance of King Richard, the Queen's son, in the aftermath of his failed campaign to take the Holy Land, and of the scheming of his younger brother John to become king--with help, perhaps, from King Philip of France. The letter, delivered by Justin after much travail, is disquieting, but at least it reassures the Queen that Richard is sill alive. There are reasons to believe that someone had hired Randolph's killers to retrieve the letter, and the Queen commissions Justin to find out that person's identity. The search involves myriad helpers--from Luke de Marston, the undersheriff of Hampshire, and Sergeant Jonas of London's constabulary, to the denizens of Gracechurch Street, where feisty Nell runs an alehouse. It's a long haul, crowned with ironic success. A graceful style, plus a plot rich in local color, puts this among the most attractive by far of the recent spate of mysteries set in medieval times.