Isaac: Why did you do this to us Derek? Was it all about the power? Were you bored? Were you lonely? Derek: Maybe. I told Cora I wouldn't leave. I'll help the others when I figure out how to help her. Isaac: There's no time! The full moon's coming. The sheriff and Melissa are going to be dead, so I'm going to help them. You can sit here and perfect the art of doing nothing.
