Last we saw Klaus, he and his siblings (save for Rebekah) had fled Mystic Falls after their mother put a binding spell on them. In Thursday's episode (8/7c, CW), he returns with a way to stay alive.
"He may have found a way [to break the spell] and is looking to implement that plan and free him up from his other siblings," Morgan tells TVGuide.com. "There's also the matter of the bag containing 12 white oak stakes capable of killing an Original that needs to be taken care of as soon as possible. So he has a two-pronged attack ready. He needs to break the spell and he needs to get hold of all of those stakes because if even one of them is left he's in serious trouble."
Fortunately for Klaus, he has another reason to keep Damon and Stefan (Paul Wesley) from killing him. "We are going to learn a very interesting fact about the Originals' mythology and the bloodlines of vampires," Morgan says. "It's not another loophole to how the Originals can't be killed, [but] it's something which has the opposite effect and it raises the threat level right up."
The Vampire Diaries airs Thursdays at 8/7c on The CW.