Complex sentence: Through Derek, they learn the body that was found was Laura Hale, Derek's sister, and the werewolf that attacked Scott is an Alpha werewolf, who is also commiting the murders throughout the season.
Split into simpler sentences: Through Derek, they learn the body that was found was Laura Hale, Derek's sister. They also learn that the werewolf that attacked Scott is an Alpha werewolf, who is also committing the murders throughout the season.