Munson was Inmate #248 in the prison in which Sawyer was also incarcerated. He was convicted of stealing 10 million dollars from the government, which was not able to be located. Munson was continually assaulted while in prison and was continually saved by Warden Harris. The Warden did this because he wanted to know where the stolen money was, presumably for himself.
Sawyer convinced Munson to trust him, because the former was correct about the Warden being cruel and also had said his wife would be used against him. During visiting hours, Munson's wife appeared and told him to give up the location of the money, perhaps for her benefit. Munson came to Sawyer with his ordeal and was horrified at the turn of events, feeling betrayed as he thought his wife loved him. Munson also confessed to Sawyer that he indeed had stolen the money. Sawyer did not seem to care until Munson told him the location of the stolen money; Sawyer had been conning Munson all along, in return for his freedom.
Sawyer later met with the Warden in the prison gymnasium. As part of a deal, Sawyer told the Warden and a Treasury Agent the location of the missing 10 million dollars just as Munson had told him (in a red Bronco at a gas station). Keeping his half of the deal, Warden Harris promised Sawyer that he would be released from prison and upon the latter's request, a share of the money would be put into a bank account in Albuquerque under the name Clementine Phillips.