{alltv} It's Vampire Diaries' Year of the Kat!

SPOILER ALERT: This story contains some key plot details from Season 2.

When we learned that Katherine was not among those unfortunate vampire souls sealed inside the tomb, it was clear that Stefan and Damon's complicated lover would show up on The Vampire Diaries at some point. Her sneak attack on Damon during the season finale was just the beginning. Season 2 promises to be, as the CW's promos shout, the year of the Kat.

"We felt like it would be really cool and powerful to bring in the woman these men loved first," says executive producer Julie Plec. "Just when you thought you were [deciding] who's right for Elena — Damon or Stefan — you add the, well, what if Katherine doesn't want any of that to happen?"

As a result, Nina Dobrev is pulling double duty this season, playing both good-hearted Elena and the Machiavellian Katherine with an unprecedented frequency. "It's hard enough to play one character, much less two," Plec says.

Katherine's arrival is the worst-kept secret in Mystic Falls, as one by one our protagonists are first briefly duped by Elena's doppelgänger. The effect is disorienting at first, but Plec points to subtle shifts in Dobrev's performances that make it clear who's back in town. "It's all told in her big brown eyes; her portrayal of Katherine, it's like the life, the good, the humanity has been stripped out of them. And then you add a couple of curly hair pieces and some mascara and you're good to go," she says.

Dobrev agrees. "It shows in the eyes, but before you get to the eyes, you've got to think differently. I'm not thinking the same things when I play Elena when I play Katherine." Her different posture and wardrobe also help complete the illusion."There's a way that I carry myself when I put high heels on that I don't when I'm in Converse."

At first blush, Katherine's master plan has an anarchical glee. "Why not go back into town and mess with your ex-boyfriend, or in this case, two of them?" Dobrev says. Eventually though, both Plec and Dobrev say that her true mission will be revealed. It promises to be a season-long journey, as Dobrev indicates that Katherine is a woman of mystery. "She's not going to give it all up and nor does she need to because she calls the shots," she says. "Everyone is and should be very scared of her."

First up, the brothers Salvatore will have to deal with the most dreaded ex of all. It's fair to say that Katherine's presence will disturb things at the most basic character level. Everyone involved with the show talks about a subtle sibling switcheroo, personality-wise.

Stefan (Paul Wesley) remains steadfast in his love for Elena and in his antipathy for Katherine, maintaining that he never really loved her. "We get to see what I like to call Badass Stefan a little bit more, you know, he's not going to take any s---," Plec says. "At this point it's not just about, 'Oh, I love Elena and I have to be her guardian angel,' it's 'Don't mess with me and this town and these people and my girl.' It's a much more aggressive stance."

Damon (Ian Somerhalder), on the other hand, is more conflicted when it comes to Katherine's reappearance and his still-simmering passions for Elena. "The fun of Damon is that any time we see the romantic leading man shining through, inevitably he'll do something to screw that up," Plec says. Indeed, Damon will perform acts both noble and treacherous in the season premiere. "He's a constant contradiction, trying to struggle against the fact that the two women that are most important in his life are causing him much grief and that his impulses are to both kiss them and kill them."

But wait, weren't two characters about to die in the season finale? It's no spoiler to say that both Jeremy and Caroline find their way back from the brink of their initially life-threatening conditions. But since this is a show that defines "living" really loosely, the future is much more complicated for both of them.

After taking a vial of Anna's blood and a fistful of pills, Jeremy (Steven R. McQueen) seemed poised for either death or a life of blood-sucking. "By the end of the first episode, we'll know whether he's a vampire or not a vampire," Plec says. Without revealing that juicy tidbit, Jeremy will continue to struggle to fit in and find some modicum of happiness, especially in the wake of Anna's death. "Happiness for him is always relative because it's usually followed instantly by tragic death," Plec says with a laugh. For now, she says, he'll make new, unlikely friendships — with people we've already met.

As evidenced by her last-minute turn for the worst, Caroline (Candice Accola) has sustained serious injuries. "She's dealing with the fact that she almost died in a car wreck, what that does to her physically and emotionally," Plec says. "We'll see a lot more of her trying to understand her own self and her relationship with her mother and her friends, and then watching where this fun, zippy girl, who has provided a lot of good comic relief, [goes] when she recovers."

It's hard being a witch on a show called The Vampire Diaries. Just ask Bonnie (Katerina Graham), whose decision in the season finale doomed many vampires to a fiery death. "Witches are always getting drawn into vampire problems," Plec says. "I think that was a line that Gram said, and that's going to be a lot of what Bonnie is going to have to deal with." Her bold stance against vampires will estrange her from Elena. An added wrinkle is that Katherine will prove to be much stronger than Bonnie, whose spells won't work when it comes to Elena's evil twin. "It poses a lot of questions as to why it doesn't affect her," Dobrev says.

Then, with a sigh, Plec turns to the subject of the other worst-kept secret of Season 2: There will be a werewolf. If the plot twist sounds familiar, it's because we've already seen the mythologies of both Twilight and True Blood introduce werewolves into their worlds. Plec is confident that her show will do it just as successfully, but she admits that it can be challenging to be in the wake of so many other similar narratives.

"You want to be able to follow all your creative instincts and then you have to turn it around and be like, 'Damn it, last night's episode of True Blood just totally did that.'" she says. "It can be frustrating as a storyteller because you actually have to adjust and reevaluate and push away from where you might naturally want to go because you're afraid of people finding it either redundant or a rip-off."

As a result, we will see how Tyler (Michael Trevino), transforms incrementally, starting with the most basic emotional shift stemming from his father's surprise death. "He doesn't understand why he's such a d---, why he's so angry and why he gets in fights with his friends," Plec says. "Now on top of that, he's a teenage boy who lost his father."

Helping him on his journey will be his uncle Mason (Taylor Kinney), who will teach him about the Lockwood family curse. "What we'll learn is that the werewolves work very hard to not give any details and not share anything in hopes of staying secret," Plec says. She hints that we won't see a full-fledged wolf for a while. Instead, in human form, they'll take on a more gymnastic affect, unlike vampires, who tend to just zip in and out of frame.

If that sounds like a lot to handle in one hour-long show, Plec says that unlike in the first season, stories will start to merge this year. "I think you'll find more integration between the human and the [supernatural] story lines," she says. "I wouldn't say that that means that everyone wakes up and knows everything about everything, but the way the characters are connected to each other will be a [supernatural] story."

Season 2 of Vampire Diaries premieres Thursday at 8/7c on the CW.