Little is known about Milton's life before the apocalypse. He was an only child, had never had a relationship and telecommuted to work. His former employment is unknown but suspected to be in some scientific field given that he conducts research on the zombies for the Governor.
While living in Woodbury, Milton studies the reanimation process of the walkers and regularly keeps tabs on various activities in town, approaching the Governor with the concerns of the townspeople. He also develops a friendship with Andrea after she arrives in town and the two begin to confide in one another concerning the Governor's long-term plans. As the Governor prepares to go to war against Rick Grimes and his group at the prison, Milton decides that he cannot stand by any longer and attempts to undermine the Governor's plans by torching several walkers held captive in pits that were going to be used against Rick's group.
DeathEditIn the episode "Welcome to the Tombs", the Governor discovers Milton's treachery and leads him into a secret torture room where Andrea has been tied to a chair. The Governor then stabs Milton repeatedly in the gut and leaves him to bleed out, knowing that he'll turn into a walker when he dies and eat Andrea.
As Milton bleeds to death, he alerts Andrea to a pair of pliers lying beneath her chair that she can use to free herself. He also urges her to stab him in the head so that he cannot reanimate. However, Andrea struggles greatly to reach the pliers and Milton dies before she can free herself. When Milton reanimates, he attacks Andrea and bites her just as she frees herself.
Later on, Rick, Michonne and Daryl find the torture chamber and a wounded Andrea. Milton's corpse lies still on the floor, apparently having been stabbed in the head.