Kit Verson was a friend of Cole Trenton since they were children.
Before he returned to America, Kit and Rick Willis were attacked by Major Matt Jones, who had been infected by a Khan worm. Both Kit and Rick were thus infected and unknowingly brought the parasite back home with them.
Shortly after, Kit begins experiencing extreme thirst. His thirst becomes so bad that he raids a Gas 'n Sip and drinks all the water he can find, and when the clerk tries to stop him, he kills the clerk and begins drinking the clerk's blood.
When Cole gets wind that Kit may have headed to his dad's old cabin, he attempts to go there alone in an effort to keep the Winchesters from possibly killing his friend. Once at the cabin, Cole notices the bodies of dead rats strewn across the floor, and while trying to appeal to Kit that he is there to help him, Kit attacks Cole and infects him with a Khan worm. Sam is able to arrive stop Kit from infecting Cole with a second worm, however Kit overpowers both men and makes his escape.
Kit returns home and starts drinking from a flower vase, which worries Jemma, who tries to talk him down, but Kit attacks her. Sam arrives in time to prevent any infection and knocks Kit out with a vase. Sam then restrains the unconscious Kit in the kitchen and explains what is going on to Jemma, when the power in the house suddenly goes out. Realizing Kit has gotten lose, Sam and Jemma search the house for him. Kit first attacks Jemma, throwing her to the ground before going after the Sam; Kit is able to take Sam down, knocking the gun from his hand, and proceeds with strangling him.
Sam however, manages to retrieve the gun and shoot Kit in the head, killing him.
In the aftermath, Sam apologizes to Cole for having to kill Kit. According to Cole, the story Jemma has given to the authorities as to what happened revolves around self-defense; Kit went crazy, attempted to kill her, so she shot him.