Upset that he has to share the room he loves with his grandfather, Peter decides to declare war in an attempt to get it back.

Peter is thrilled that Grandpa is coming to live with his family--until Grandpa moves into Peter's room, forcing him upstairs into the creepy attic. And though he loves his grandpa he wants his room back, so he has no choice but to declare war. With the help of his friends, Peter devises outrageous plans to make Grandpa surrender the room. But Grandpa is tougher than he looks. Rather than give in, Grandpa plans to get even.