Friendship, courage and ingenuity are put to the test once again as Pertsa, Kilu and Pirkko embark on an epic adventure to solve the mystery of an old map. Twin girls Vappu and Kerttu also join the flight, and the suspense is increased when the cunning criminal Annabella Pehko jumps on board as a stowaway.

Pertsa and Kilu are two neighbour boys with different backgrounds. They live adventurous life of a young imaginary mind in small harbour town. Accidentally they get involved in a bank robbery. Through their own investigation of the case, imagination and real danger gets mixed and leads to great adventure where friendship and courage is on stake.