Emile is invisible

The clues: A knitted sock with the word Torvik inside, a small rock, a wooden dragonhead The file label: "It Was Them" The investigation: The sock clue leads Kyla to a group of re-enactors called Torvik. After learning some basic sword fighting moves, she discovers that the sock was made using a knitting technique called nalbinding, which is how Vikings made socks and mittens. The kids wonder if this mystery might be about Vikings. E.B. heads to a Viking archeology lab to investigate the rock. Turns out It's a piece of slag iron, which is what was left over after the Vikings made iron. He helps forge a rivet just like the Vikings did for their awesome ships! Kyla discovers there's a Viking ship at sea right now. It's the biggest modern day Viking ship ever built. She video chats with a crewmember aboard the ship and finds out that the dragonhead clue from the mystery file is almost exactly like the dragon figurehead on this ship. Vikings used to put dragon figureheads on their shi