Faith and the Law #3: The Holy Roller - James J. Griffin

Father Tad, now in the guise of his Texas Ranger brother Chaz, faces a long and dangerous journey to get his prisoner to Austin. Once he arrives in the capital city, he realizes he needs to get more evidence against the criminals his brother was trying to bring to justice, before he was ambushed. His search will lead him into an exclusive gambling den, which is secretly owned by some of the most powerful men in Austin.

(This serial novel keeps getting better with each installment, and it's still early enough in the game for you to catch up easily if you haven't started it. The explosive climax of this chapter has me eager to read the next one!)