 Playing alone one night while his parents are on vacation, twelve-year-old Victor Laroche (Tommi Ohrner) glimpses a mysterious masked man behind him in the mirror and soon begins to uncover a mystery surrounding the death of a girl named Cecilia who fell over a stair railing in the house 20 years earlier.Although not entirely convinced of his story, Victor's sisters Cora () and Louise () agree to help him investigate the girl's mysterious death.With the help of an elderly uncle who was Cecilia's father () and an old friend of Cecilia's (), the Laroche children piece together the mystery of the death of their cousin, the unknown man in the mirror, and a little leather crocodile they find with strange gleaming eyes.