The Thea Sisters are taking a trip to Canada. They have been invited to do some bird-watching with a group of friends. The girls are enjoying learning more about Canada and their love for hockey. But during their trip, one of their group members mysteriously disappears. They set off to Niagara Falls to find him. Can they solve the mystery?

Geronimo Stilton is the pseudonym of the famous Italian writer Elisabetta Dami. She has written the famous series of books on Geronimo Stilton. She co-owns the Italian based publishing company called Edizioni Piemme. She likes to get all her ideas through her travels to places around the world.