Careful plotting, strong characters and a wealth of period detail distinguish the latest adventure of itinerant peddler and sleuth, Roger the Chapman, from British author Sedley (The Lammas Feast). As the gloomy winter of 1478 draws to a close, Roger is returning home to Bristol when he stops for the night in a village haunted by old mysteries. Six months earlier, a local siren, Eris Lilywhite, disappeared after humiliating her betrothed by consenting to marry his father instead. At Eris's grandmother's request (and despite the hostility of Eris's mother), Roger agrees to stay in Lower Brockhurst and investigate. His efforts to connect the girl's disappearance with other events in the village, both past and present, parallel the old parlor game, Nine Men's Morris, in which two opponents each try to form a line of three markers on a rectangular grid. Roger's instincts and medieval superstition occasionally collide with his more rational, logical side. Peasant characters at times think in ways inappropriate to their humble status ("The Papal Commissioners don't venture into the wilds very often, and when they do, sand is thrown in their eyes"), but in every other respect the author is true to period. Sedley pens medieval historicals as fine as those by better known names in this subgenre, including Edward Marston, Alan Gordon and Candace Robb. (Aug.)