Tough, naughty, quick-witted and brave Lillebror has just moved, and has not made any new friends yet, when his imaginary friend – the wooden twig Knerten – appears in the middle of a pile of firewood...

Little Brother has moved with his family, and a stick son has seen the day of light, but there is no new friends.

When Lillebror's mother is mysteriously hurt in a biking accident, Lillebror and Knerten turn the town upside down trying to find the culprit.

Lillebror moves with Twigson and his family to the western part of Norway, but he dreams of even bigger expeditions, like going to the North Pole.

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.