The Ghost of the Luna Park

Detective friends Arthur, Rosa, Viola, and Luke came to the capital for their vacations.

Besides sightseeing, they were planning to celebrate Rosa's fifteenth birthday.

But their celebration was interrupted by... a ghost. The kids have evidence - photographs showing a pale silhouette roaming through the Luna Park. 

The friends are confused - it is well known that ghosts do not exist, but the photographs are real. Therefore, they begin an investigation to find out: do ghosts really exist or is this someone's cruel joke?