"Sabina Carpenter and John Quinncannon are no stranger to mysteries. In the five years since they opened Carpenter and Quinncannon, Professional Detective Services, they have solved dozens, but one mystery has eluded even them: Sherlock Holmes or, rather, the madman claiming his identity, who keeps showing up with a frustrating (though admittedly useful) knack for solving difficult cases. Roland W. Fairchild, recently arrived from Chicago, claims...