Ep 8. It Only Comes Out At Night

Jack, Hannah and Moustapha try to unravel the "Loch Ness Monster" -style mystery of a nocturnal creature, roaming the streets of City in the Sea and capturing its citizens. Despite difficulty from Scharnhorst, who doesn't believe the creature exists, they discover that it's a special kind of dinosaur called a Thecodont, and it's capturing the city-dwellers to use as food for its young.