Berend Botje is a tough girl with a lively imagination. She is the youngest member of the mysterious captain family Botje, which also consists of father Berend and grandfather Berend. The Botjes' adventures are so special that no one believes they really happened. But Berend knows better. When the city falls under the spell of an unusual bird egg, she is convinced that it is a Knoetel Egg, which only opens on a hidden island. She decides to make the daring trip to the island herself. Because nothing is impossible for Berend.