The introduction to this novel contained some details which are now not considered part of the Ellery Queen canon. For instance, the introduction is written as by the anonymous "J.J. McC.", a friend of the Queens, and speaks of Ellery's marriage and child, and their life in Italy, and that the names of both Ellery Queen and his father are pseudonyms—none of these circumstances survived for long. It also mentions a novel called "Murder of the Marionettes" (page 184 of the Signet paperback edition in Chapter 27) which purports to have been written by the detective Ellery Queen, not the writer of the Ellery Queen novels themselves; this novel does not exist and is not mentioned again.