"The Roman Hat Mystery" established a reliable template: a geographic formula title ("The Dutch Shoe Mystery", "The Egyptian Cross Mystery", etc.); an unusual crime; a complex series of clues and red herrings; multiple misdirected solutions before the final truth is revealed, and a cast of supporting characters including Ellery's father, Inspector Richard Queen, and his irascible assistant, Sergeant Velie. What became the best known part of the early Ellery Queen books was the "Challenge to the Reader." This was a single page near the end of the book declaring that the reader had seen all the same clues Ellery had, and that only one solution was possible. According to the novelist and critic Julian Symons, "The rare distinction of the books is that this claim is accurate. There are problems in deduction that do really permit of only one answer, and there are few crime stories indeed of which this can be said."