Best friends Bětka and Alma are spending a dull summer at a lakeside with Bětka’ s older sister Marie. The teenage girls want to experience something big but their efforts fail until they discover a mysterious pool on an island.

At Strašperk Castle, the royal budget is being improved by spooky tours instead of raising taxes. These are directed by the resourceful princess Elvíra. Prince Armin arrives at Strašperk, eager to see a magical creature to prove to his royal father that they really exist. As a little boy, he met a witch in the forest, but his father never believed him. Soon, an unexpected event occurs at Strašperk - during the celebration of the king's birthday, the musicians disappear without a trace, then some servants, and finally the king himself. Panic breaks out in the castle. Elvíra and Armin set out to follow the trail of this mystery. It turns out that things are often not what they seem at first glance. And when it comes to magical creatures, no one knows when the next one will be born.