While the excavation continues, Peter and Elroy return to the investigation to clear Olof's name. They meet a professor who gives them new knowledge about the area and the history of his tribe.

With many new clues to follow, they head to the east coast to take a closer look at rock engravings that can provide more answers. They meet the historian Sturla Ellingvåg who takes them on a boat trip.

They finally get to see the famous Maine Penny, and the visit to the Maine State Museum opens their eyes to new opportunities. Afterwards, they meet the anthropologist Harald Prins.