Jon Anderson was a Human Starfleet security officer who served in the 23rd century. He was born on a far-out colony on Sachem IV and in the 2260s, Anderson was the only resident of Sachem IV to serve in Starfleet.
In mid-2266, the Klingon Defense Force targeted Anderson for replacement by an undercover agent, due to Anderson's respective isolationism from anybody who would know and recognize him. After following Anderson for a while he was captured and eventually killed, and Klingon Imperial Intelligence selected Kell to replace him. The exchange went smoothly and only his mother noticed that it had been several weeks since she received a communication from her son. (TOS - Errand of Vengeance novel: The Edge of the Sword)