“The Walking Dead’s” new Season 4 threat has been revealed, and it’s pretty terrifying. The virus might not have a face as gruesome as the walkers do, but its ability to strike down anyone infected with it in as little as a day means that it’s the survivors’ most difficult enemy to defeat yet.

After having a very clear enemy in Season 3 in the form of the Governor, Season 4’s virus gives “The Walking Dead” a different sense of momentum. It’s something that leading lady Sonequa Martin-Green, who plays Sasha, found very exciting when the plot twist was revealed to her.

“I thought it was a brilliant move. I love that this world can continue to surprise you,” she told Zap2it at “The Walking Dead” Season 4 premiere. “A show loses its fire, it loses its fervor, when everything is familiar to us, and I think this virus is the perfect example of keeping it moving and keeping it unpredictable and keeping this sense of danger alive. Although it might seem like we have a semblance of security, we don’t.”

So does she think the virus is more terrifying a threat than the walkers or the Governor? Martin-Green isn’t going that far. “I would say, I gotta go with the walkers, because that’s the show, right?” she says with a laugh.

As for Sasha’s new role in the Council, Martin-Green gives a bit of context for the change of leadership in between Seasons 3 and 4.

“That happens in the time that’s lapsed between the end of 3 and the beginning of 4, and it’s sort of just emerged,” she explains. “The Council, it is just what happened. Sasha arose as someone who could lead it, and there we are. ”

“The Walking Dead” airs Sundays on AMC at 9 p.m. ET.

Posted by:Terri Schwartz