Cardinal Ratcliffe arrives in Kembleford from Rome, with Vatican police inspector Mario Angelini, on a mission to finally find the St. Sylvester papal tiara, lost since the fifteenth century. The last known trail is to the nearby castle and ancestors of Lady Cecily. Brown accompanies as spiritual advisor Lady Felicia , who poses as an imaginary aristocratic bride inspecting with Mrs McCarthy, posing as her mother, the estate as venue for a socialite wedding to an American tycoon. Master thief Flambeau poses as that groom, complicating the room assignments. Brown is reluctant to team of with the career scoundrel, yet will even risk excommunication rather then trap him to risk the death penalty. A vindictive viper bites, the clue hunt leads to the treasure and a dangerous finale for all.
—KGF Vissers