Carlos Medina has his hands full controlling his unruly pack, especially when his wolves are plagued by some sort of health condition preventing them from acting like proper predators. Not that Carlos is a shining example. With his high cholesterol levels, he can't deal with both his health and an invading enemy wolf pack.
The enemy offers a one-on-one fight to the death, and Carlos accepts to save his wolves. When he finds out his opponent is the man who shattered his heart long ago, he's only happy to rip out Reed's throat.
Reed Williams has always placed the needs of his pack first. When Reed sees it's Carlos he has to fight, he decides it's about time he placed his needs ahead of his pack. All that's left is preventing his old mate from tearing him apart.