The fifth movie about the wooden pin Knerten, who this time is going on holiday to a lake where there's seen a sea monster.

Knerten feels neglected when Junior and his caring big stepbrother Philip go to summer camp on a 'magical' island. Philip encourages Junior to make new friends, which works out with Eddy, as the pair are fascinated by adult Blegen's stories about the legendary sea snake monster in these waters.—KGF Vissers