Uh-oh. Frank isn't doing well at school, and he has just been told off by his head teacher again. He has one last chance to prove himself: all he has to do is follow the rules on his class trip to Chiltern House, complete his worksheet and stay out of trouble. But when a girl steps out of a painting and steals Frank's worksheet, staying out of trouble is easier said than done. Together, they embark on a perilous adventure to discover the girl's lost identity, uniting with new friends along the way who show Frank all is not as it seems in this stately home.