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." lasts only through the tenth novel, "Halfway House", then vanishes (though J.J. appears onstage in "Face to Face" in 1967).