Postal Station Ratskhof. Vol. 1. The Labyrinth of the Dead

Ninth grader Olya Goncharova helps her parents, who run
a postcard shop in Kaliningrad, and is actively engaged in postcard cross-posting. The international exchange of postcards seems like an innocuous affair, but everything changes when an antique card accidentally arrives in... the Goncharovs' mailbox a week before the autumn holidays. Olya suggests to her friends — Nastya, Hammer, and Gleb — to create their own detective agency to unravel the mystery of the unknown sender. What they began as a playful investigation, more resembling a library quest, quickly becomes serious and leads them on a dangerous journey. The heroes find themselves in a real "labyrinth of the dead," and the closer they get to the solution, the more often Olya wonders whether it was really just by chance that the card,
marked with a stamp of an Egyptian vulture, ended up with her.