Lonesomen: The Ties of Blood (Lonesome #3)

Markham, the murderous preacher, is dead at last. And yet, for the lone rider who tracked him down and killed him, the hunt goes on. Now he must find the person behind the preacher's campaign of terror. He knows his target: Senator Dawson of New York. But it won't be easy getting to his quarry - a rich and powerful man engaged in a conspiracy against the government of the United States, who may just hold supernatural capabilities...