The introduction to this novel contained a detail which is now not considered part of the Ellery Queen canon. The introduction is written as by the anonymous "J.J. McC.", a friend of the Queens. Other details of the lives of the fictional Queen family contained in earlier introductions have now disappeared and are never mentioned again. The introductory device of "J.J. McC." disappears after the novel following this one, "Halfway House"—though a character named "J.J.," a "Judge McCue," appears as a friend of the Queens in the much later novel "Face to Face."