Banker's Gamble — James J. Griffin

Tim Bannon is en route to the town of Rankin, where the bank has been robbed and the town marshal killed.
Still a day's ride from town, he stops for the night at a pond. While taking a swim, he is accosted by a gunman who tries to kill him. After a fierce fistfight, Tim manages to get to his gun just in time, and shoots his would-be killer. Evidence Tim finds in the man's saddlebags gives him his first hint as to who was behind the bank robbery and marshal's murder.
But can Tim find the proof he needs before he himself is the victim of a bullet in his back?