This is Antek's last holiday in Masuria, at the house of his recently deceased grandmother, Ela. No more adventures and treasure hunts that his grandmother organized every year for him and his local friends - Jagoda and Karol. "This year will be the most boring holiday of my life," Antek thinks, at least until he finds a mysterious message in the mailbox from... Grandma Ela. This is the beginning of the last adventure together, which Grandma Ela planned before her death. Antek, his step-sister Maja, Jagoda and Karol throw themselves into the vortex of surprising events, not expecting that this time they are not the only ones looking for the treasure hidden by Grandma Ela.
—G