This time, they travel on holiday with Aunt Thea to Summer Island. There they meet Eddy who is an expert on all the challenges they can face on a magical island. It is rumored that a sea worm has been observed in the fjord, and it will not be long before the energetic sea worm expert Blegen shows up, with his strange devices and instruments. It will be an exciting summer holiday with friendship put to the test, exploration in nature and the hunt for the mysterious sea worm.

Norway, 1204. A civil war between the birkebeiners —the king's men— and the baglers —supporters of the Norwegian aristocracy and the Church— ravages the country. Two men must protect a baby, the illegitimate son of King Håkon, who will be the future king and peacemaker, from those who want to kill him.