Deputy Sheriff Rick Grimes wakes up in the hospital, after being shot, to find his town overrun by flesh-eating zombies. After making friends with survivor Morgan Jones and his son Duane, Rick sets out to find his wife and son.
While searching for Merle, Rick and the others come across another group of - seemingly hostile - survivors. Meanwhile, back at camp, Jim is deeply disturbed by a dream he cannot fully remember, a dream which may turn out to be prophetic.
The survivors deal with the aftermath of the walker attack and decide to move to the C.D.C., hoping to find a cure for an infected Jim. Meanwhile, Shane - finding his leadership position challenged by Rick, succumbs to his inner demons.
At the C.D.C., Rick and the others find Dr. Edwin Jenner, a scientist who is on the verge of suicide. But just when they think they're safe, Jenner tells them that the building is on a countdown to self-destruct.