The promo shows Mika being chased by Lizze who is dressed as a walker. The synposis indicates that the Grove appears to be an ideal place to set up camp but the survivors, especially Carol, wonder if they can go back to the way things were. Viewers will find out that Lizzie killed the first plague victims. Lizzie's will display new symptoms of conduct disorder beyond animal mutiliation and possible murder. Perhaps she will bite her sister Mika. What happens if a human bites another human?. Since humans are infected perhaps their victims will get the fever and die.
A second promo dwells on this theme of whether some people are too far gone so this will be the theme of this episode.
In another sequence, we see Mika being attacked by walkers. Perhaps she is just dreaming because her sister scared her by pretending to be a walker.
In another promo, we see Tyreese moving toward a limping man who appears to be dressed in the same clothes that Rick was wearing. Chances are it's not a walker, it's Rick.