In Rivals and Retribution, the fifth book in the 13 to Life series by Shannon Delany, Pietr and Jessie will find themselves caught in a pack war with a new breed of werewolves.

 
Jessie Gillmansen is in trouble again and she's in for the fight of her life--and Pietr's! With Marlaena’s dangerous wolf pack putting more pressure on the Rusakova family, change is inevitable and when it comes, it brings a heavy price that forces Alexi into action to save his youngest brother's heart, head, and life. In the stunning conclusion of this celebrated paranormal series two werewolf families fight for control of the small town of Junction, control of each other and--most elusive of all--control of themselves.