The Skeleton of a Sperm Whale

Finally, brother and sister Emma and Lucas have arrived at the Whale Museum! There, they got to know many inhabitants of the North Sea and even saw the skeleton of a real sperm whale. But what is this? The ribs of the sperm whale are fake! Soon, the young detectives are on the trail of a suspicious gang dealing in whale and sperm whale bones. These "large fish" Emma and Lucas will certainly not let slip away...