When Federal Marshal Buck Fyffe was charged with taking the outlaw Luther Gibbs to Yuma Territorial Prison, he wasn't expecting any problems. But it doesn't take long for Gibbs's gang to find them and Fyffe is overtaken by the gang. The gang hatches a plan for Gibbs to pose as Fyffe, and to deliver Fyffe to Yuma prison, claiming he is Luther Gibbs. Fyffe finds himself as prisoner number 109 and must survive in a prison where he'll surely be recognized by someone he sent there.