The Hesperian Dragon — Brendan Carroll

The Chevalier Mark Ramsay, Assassin and Alchemist for the Red Cross of Gold goes after the lost Key to the fabled Ark of the Covenant and in the process, discovers that the Order has attracted the attention of the Ancient Order of Assassins, a far eastern cult and long time enemy of the Knights Templar. He is only days away from marrying his one true love when he is torn away from her by his obligations to the Order and his beloved Brother, Lucio Dambretti. He finds himself in Divine company, fighting for his life against a terrifying dragon.