Thirteen-year-old Jack Sullivan has survived the monster apocalypse alongside his genius best friend, Quint; reformed middle school bully, Dirk; lone wolf survivor, June Del Toro; and Jack's loyal pet monster, Rover. When the kids run into trouble, a talking monster named Thrull saves them and leads them to Joe's Pizza, where a whole host of friendly monsters are living. When Thrull finds out Jack and his friends destroyed Blarg, a servant of the evil Rezzoch (voiced by ROSARIO DAWSON), he gives the kids a magical bestiary and tasks them with filling it with the essence of every monster they can find. While completing their new mission, the kids realize that something is luring zombies to their death. Can the gang crack the case and complete the bestiary? Or will something--or someone--stand in their way?