This semester at Bloor’s Academy brings a few changes. There is a new art teacher, Mr. Boldova, and a new student named Belle, who lives with the Yewbeam aunts and seems to have strange power over them. Emma and Charlie soon discover Mr. Boldova’s secret identity: He is the older brother of Ollie Sparks, the boy who lives in the attic of Bloor’s Academy. Ollie had always been prying into matters that didn’t concern him, so Ezekiel Bloor had made him invisible. When Charlie and his friends find him, Ollie is alone and hungry, so they promise to help him become visible again.
Elliot, grieving for his dead mother, is sent to stay with his cousins. There he is haunted by Mary-Ellen, who was once kept prisoner in his room. The loss of her fiance, Orlando Rinaldi, killed in World War I, threatened her sanity - or so everyone thought.
Lonely and friendless from constantly moving, Dinah finds herself wishing the animal statues protecting a nearby Welsh castle would keep her company. Suddenly, to Dinah's delight, the stone animals start to magically spring from the walls and follow her home. But when the animals refuse to let Dinah leave her house, she quickly realizes that these mysterious creatures aren't rescuing her, they're imprisoning her. . . .
When Elly and her family come to look after aunt's house, she sees at once that Stone Mouse is special, but her brother Ted says he's just a dirty old pebble. But then Ted is angry with everyone and everything - and as Stone Mouse soon discovers, that means trouble.