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...
Koko moved to the city with his parents. The apartment they relocated to used to belong to an old cheap man, whose death is surrounded by a veil of mystery. Do ghosts really exist and will Koko be able to solve the mystery with the help of his friends? His sister, faithful dog, a wise inspector and their worried parents will all be involved. Will Koko be able to solve this riddle before all the adults, we'll find out in the boisterous denouement of this detective story.
