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.

Rick makes a decision to go back to Atlanta to retrieve the bag of guns and save a man's life. Lori and Shane must deal with the surprising return of someone they thought was dead.

Rick's mission to Atlanta is jeopardized when things go awry. Jim becomes unhinged in camp.

Rick leads the group to the CDC after the attack. Jim must make a terrible life and death decision.

Rick and the group are allowed into the CDC by a strange doctor, but all is not what it seems in their newfound haven.