After a young boy moves from Zeleni vrh to Zagreb, he starts to reveal mysteries about his new house. Soon Koko and his friend, Zlatko, are deep into their investigation...After a young boy moves from Zeleni vrh to Zagreb, he starts to reveal mysteries about his new house. Soon Koko and his friend, Zlatko, are deep into their investigation...After a young boy moves from Zeleni vrh to Zagreb, he starts to reveal mysteries about his new house. Soon Koko and his friend, Zlatko, are deep into their investigation...