sentences:  The character of Ellery Queen and the more-or-less locked room mystery format were probably suggested by the novels featuring detective Philo Vance by S.S. Van Dine, which were very popular at the time.This novel was the second in a long series of novels featuring Ellery Queen, the first nine containing a nationality in the title.The introduction to this novel contained some details which are now not considered part of the Ellery Queen canon.