 Peter and Derek reveal to Isaac that Derek was building a pack to combat the impending Alpha Pack and Peter knows that they have arrived.Also appearing during the season are Dr. Deaton (Seth Gilliam), Adrian Harris (Adam Fristoe), Coach Bobby Finstock (Orny Adams), Sheriff Stilinski (Linden Ashby), Danny Mahealani (Keahu Kahuanui), Marin Morrell (Bianca Lawson) and Mr. Lahey (John Wesley Shipp).Kali, Ennis, Ethan and Aiden make a brief appearance in the season finale, "Master Plan", as the members of the Alpha Pack that kidnapped Boyd and Erica.