Since the phenomenally successful Walking Dead started four seasons ago, it has always been about zombies eating people. Zombies have been a consistent part of the Walking Dead universe. Most of the time, zombies are easy enough to kill and are not exactly formidable enemies. They die from a rock, a stick or even with just bare hands. Even their own flaws are the reason why sometimes get people killed. They are unluckily careless, greedy or panicky.

In the season premier, killing zombies has already become a household chore. The surprise comes in for the first time when Sheriff Rick and Merry Band need to contend with something else. A different kind of foe killed Patrick, whatever it was. It attacks from within and basically invisible. After an insidious disease begins to spread in the prison, drastic action is taken to segregate the healthy from the infected.

The true nature of this new threat and which Zombie Force members are best suitable to handle it will be revealed in the coming days. Will Carol's careful and sometimes mean decision-making hurl Michonne's excellent sword power? How will this play into Daryl's hesitant acceptance of leadership or Glenn's paranoia? Will Carl's innocent and blissful childhood be cut short? Is Herschel's poignant wisdom outdated in this new world? How will all this affect Rick?

Who could the Walker Feeder be? It acts like a malevolent dark force unlike the all-consuming drive of the undead. Is it responsible for pouring gasouline on Karen and the unidentified man to set them ablaze, killing both of them and their viruses? What is the cause of flu virus? When will the Governor show up again? Can anyone survive in a Zombiepocalypse?

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The people on the show have been predictable in that often dishonest, selfish and downright crazy behavior. It was oddly comforting to know that just as zombies are always slow and relentlessly bad and a different kind of enemy is a bit of a gamble for the show. The clarity of the zombie and human battle lines is quite appealing for viewers but this seems to have changed in Season Four.