The lack of progress in the investigation of a series of brutal killings is taking a mental toll on the Hampstead police department. Psychologist Peter Collins is brought in to help build a profile of the murderer, but his unconventional methods involve dissociative episodes in which he consults with Lord Peter Wimsey (yes, the fictional detective created by Golden Age mystery novelist Dorothy Sayers). Although the police are initially skeptical, they begin to suspect Wimsey may prove the key to cracking the case. What Would Wimsey Do? is engagingly paced with a resolution that few readers will guess. (BH)