The Walking Dead takes place after the onset of a worldwide zombie apocalypse. The zombies, colloquially referred to as "walkers", shamble towards living humans and other creatures to eat them; they are attracted to noise, such as gunshots, and to different scents, e.g. humans. Humans that they bite or scratch become infected and slowly turn into walkers as well.
The series centers on sheriff's deputy Rick Grimes, who wakes up from a coma to discover this apocalypse. He becomes the leader of a group of survivors from the Atlanta, Georgia region as they attempt to sustain themselves and protect themselves not only against attacks by walkers but by other groups of survivors willing to assure their longevity by any means necessary.
Rick searches for his family after emerging from a coma into a world terrorized by the walking dead. Morgan and Duane, whom he meets along the way, help teach Rick the new rules for survival.
Rick unknowingly causes a group of survivors to be trapped by walkers. The group dynamic devolves from accusations to violence, as Rick must confront an enemy far more dangerous than the undead.
After returning to the camp with the department store survivors and an emotional reunion with his wife and son, Rick decides to go against Shane's advice and go back to Atlanta for Merle Dixon and his dropped bag of guns accompanied by Merle's younger brother, Darryl Dixon, as well as Glenn and T-Dog.
While still in search of Merle, the group tries to retrieve the bag of guns but are attacked by several living men who are also after the weapons. The group manages to grab the injured attacker; however, several of the attackers escape and take Glenn hostage. Back at camp a large group of walkers venture up the hill and take the survivors by surprise.
Rick leads the group to the CDC after the attack on the camp. Jim must make a terrible life and death decision.