The Plague of Thieves Affair — Marcia Muller; Bill Pronzini

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 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 Holmes is his first cousin, Charles P. Fairchild III. Now, with his father dead, Charles stands to inherit an estate of over three million dollars-if Sabina can find him, and if he can be proved sane. Sabina is uncertain of Roland's motives, but agrees to take the case.

John, meanwhile, has been hired by the owner of the Golden State brewery to investigate the "accidental" death of the head brewmaster, who drowned in a vat of his own beer. When a second murder occurs, and the murderer escapes from under his nose, John finds himself on the trail not just of the criminals, but of his reputation for catching them.

But while John is certain he can catch his quarry, Sabina is less certain she wants to catch hers. Holmes has been frustrating, but useful, even kind. She is quite certain he is mad, and quite uncertain what will happen when he is confronted with the truth. Does every mystery need to be solved?