The Parisian Prodigal — Alan Gordon

In 1205, Theophilos -- a fool by trade, a family man by choice, and a spy by design -- belongs, along with his family, to the Fools' Guild, a group that secretly maintains the fragile order of society. In Toulouse, that order is threatened when, unexpectedly, a man claiming to be a full brother of the ruling count is found one morning in a local bordello next to a dead whore, killed with his own sword. Now, Theophilos and his family must uncover the truth.