Three kids, raised by wildlife specialists, are sent to the town of Gruselbrook to live with their Grandfather for the summer. They soon realize that Grandpa Arthur is a genuine Monster Hunter who has spent a lifetime battling the supernatural. But the old man is not as able as he used to be, and though he has difficulty admitting it, some new blood is sorely needed. Arthur invites his grandchildren on a journey of training and discovery to become the next generation of Monster Hunters. But whenever Grandpa falls asleep on the job, which the old man often does, our young heroes get busy with their own rebellious agenda: These kids don't want to hunt the monsters. They want to save them.