This is the twentieth Cyrus Skeen detective novel. Skeen and his artist wife, Dilys, plan to have a quiet Christmas together, but then Skeen is suddenly invited to speak before a sociology class about his "Trichotomy" article in the American Mercury, which appeared in August to great acclaim. His essay is about criminal motives and the psychology of recidivists, or repeat offenders. He has finished the second part of the essay, which will appear in the spring. Skeen, a noted private detective with an impeccable and effective record of dealing with recidivists, agrees to field questions from the students about the subject, but then things go murderously wrong in the classroom. The wrong man is murdered.