The Walking Dead - The Walking Dead: Season 2
Luke has been betraying the group all along. That's why he ditched Kenny, because he KNEW Carver and their people were coming.
He was super nice to Clem, and even Carver seemed to admire qualities in her. Maybe they were "grooming" her so to speak. Carver knew exactly when to come by to scout when no one was there...why do you think that is?
Luke betrayed the group and that's why Carver was able to track them so easily/quickly. For all Kenny haters, sorry, Kenny may be unhinged right now, he may not trust Luke and the cabin group, but he did not kill Luke. He may be unhinged just a bit, but he's not a murderer.
Luke, as nice as he seems, almost seems TOO nice.