The Secret of the Camellia Medallion

Autumn vacation for sixth grader Alya could have been the most boring if not for...
If not for someone unusual in the entrance of their old house, frightening the neighbors. But unlike the neighbors, Alya does not believe in ghosts. Can a ghost leave such huge traces behind? Or is it someone's trick to confuse? It seems to be connected to a precious medallion that this someone is hunting for. Alya is about to embark on a dangerous investigation, as the chain of mysterious events goes back to the last century and weaves through St. Petersburg's entrances, a dilapidated attic, and even a used bookstore.