It is late June, 1929. Cyrus Skeen has concluded his case in Stolen Words, in which he exonerated a prominent novelist of the charge of murder, even though the author had plagiarized other authors with the cooperation of the now defunct publisher. Skeen's artist wife, Dilys, has returned from a visit to relatives back East in Massachusetts, and was preparing to work on her first painting. Skeen's new secretary, Lucy Wentz, is quick on the uptake, and is working out fine. But now a new nemesis has confronted Skeen, an unknown person who is killing people who have committed horrendous crimes. He writes Skeen and expresses his appreciation for Skeen's crime-fighting acumen and skills, but wants Skeen to join him in a crusade to terminate all killers. Skeen has not killed any criminal gratuitously - he has killed in self-defense only when someone has threatened to kill him or someone who is a value to him - and wonders why his admirer thinks he would be open to the idea. Then the district attorney for San Francisco demands an explanation for why Skeen's revolver was found next to a murdered mass killer. More criminals are found dead. The unknown vigilante pins a note to each body, signed "Exegesis." In another unusual case tackled by Cyrus Skeen, the intrepid and unflappable detective delves into the mystery with his usual panache and certitude.