The Unseen - L. J. Smith

The greatest threats are the ones unseen.... For what seems like the first time, Elena and her friends are happy. Elena and Stefan have built a home for themselves in Dalcrest, and all of Elena's friends are as in love as she and Stefan are. Even Damon is enjoying visiting his favorite old haunts in Europe, and is more surprised than anyone that he's traveling with Katherine. But lately, Elena's Guardian senses are on edge, and she can't ignore the feeling that danger is coming. When a new threat arrives in Dalcrest, Elena's worst fears become a reality. Soon, she and Stefan are battling a vicious Old One who is always just out of their reach. And when Damon and Katherine are confronted with a strange and mysterious enemy, Elena worries the attacks are linked. As dark forces close in, Elena, Stefan, and Damon struggle to survive the only way they know how--together. But their lives are hanging in the balance, and every moment they share could be their last....