"Walking Dead" season 4 premiered last Sunday, and fans are already looking forward to "Walking Dead" season 4 episode 2. Titled "Infected," it will air next Sunday on October 20.

AMC has released the official synopsis for "Walking Dead" season 4 episode 2:

 "The group faces a new enemy; Rick and the others fight to protect their hard-won livelihood."

It sounds like the new threat to the group is finally going to make its first appearance. It is not an additional zombie threat according to "Walking Dead" creators, but is more related to mother nature.

 "A non-bite-related death occurs this episode to a character who is isolated from walkers. No bite on that guy, but he turns nevertheless. He isn't the only one, either; just the most obvious example." We already know that people turn when they die, bitten or not, but it's still unclear whether these deaths are natural or ... unnatural," says a teaser from comicbook.com.

Some photos of the "Walking Dead" season 4 second episode show Daryl with a bandana covering his nose and mouth, possibly as a response of self-preservation after an outbreak of something. A flu? A virus? The title doesn't say "Infected" for something light!

"Walking Dead" season 4 episode 2 spoilers also indicate that something has been going awry from within the prison-somebody from within is sabotaging attempts to keep safe by putting dead rats on the fence to feed the zombies.  "There's a B plot in this episode, too, and it's one that's far more intriguing than [the premiere's] various romances. There's an enemy within, to borrow a previous episode title, and it's not clear who it is or to what end they're acting - but if not for the generalized threat presented by the episode's major development in Cell Block D, that sub-story could very well overtake the show."