Regina is a nimble, grey-haired and clever rat. She can read and has an unusual job for her species: she works as a tour guide and shows rats the beauty of her hometown Prague. However, Regina is sad. She knows that rats do not live long and that her last beloved hibernation is imminent. In addition, her life has become boring because the tourist rats stayed away and she can hardly do her job anymore. Together with her brother Rudolf, she embarks on a search of a mysterious, medieval elixir that is supposed to double the length of their lives. To find recipes and ingredients, they walk through old pharmacies, into the catacombs of the Old Town Hall, on the floor of the Old-New Synagogue and to the Vltava River. Can Regina and Rudolf prepare all the ingredients correctly and does the potion work at all? Have fun on a completely different journey of discovery through the Golden City of Prague.