Rumour has it that the school is haunted by a ghost called Annie. The only problem is that no one has ever seen her. Is it just a rumour? Or does Annie really exist? Sam and Donna, pupils at the school, think they might have solved the riddle when they unexpectedly discover part of a Roman mosaic in the school grounds. The mosaic shows a young girl and both children are convinced that this must, indeed, be the face of the mysterious ghost. But how can this be proved? Disaster strikes when a building firm moves on to the land where the mosaic was found. At which point Sam and Donna realise the only way they can save the mosaic is to confront Lauren, the school bully. Can the children stop the destruction of the mosaic, face up to Lauren and solve the riddle of Annie?