Olive and Franek have always loved holidays by the sea. This time, however, they weren't going to a normal resort - their parents had rented a small house right next to an old cliff for the whole summer, which no one looked into in the summer. Right next door stood an even older lighthouse, which, according to the locals, had long since ceased to function and was due to be demolished. But on the first night, when the wind moved the shutters, Olive could not fall asleep. She had the impression that quiet laughter could be heard among the sound of the waves and that some strange shadows were circling around the lighthouse. The next morning, Franek had already been asking his sister from dawn if she wanted to go on an expedition. And so, armed with binoculars, a notebook and a torch, they slipped out after breakfast. The closer they got to the lighthouse, the more disturbingly intriguing it seemed - something colourful was flying from a window at the very top, like a fragment of an old flag, and a twisted staircase led up to a solid padlocked door. - 'Look, there are strange footprints here,' whispered Franek, pointing to the wet sand beneath the window. The footprints were small, perhaps from a bird... but still next to them they discovered a strange feather shining blue. They decided to wait until everyone had returned to the beach - then they could investigate the area around the lighthouse more thoroughly. They holed up under a small oak tree right next to it and took note of every disturbing sound and every gust of wind, which brought with it completely new and unprecedented smells by the sea, as if someone was cooking cinnamon cookies. Suddenly they heard a soft clatter from the side of the door. Something shimmered under the handle - it was a small, old keyhole that was definitely no match for an ordinary padlock. Frank slipped his finger in and, to their amazement, the door swung open with a quiet creak. The inside of the lighthouse was filled with light that pulsed like the breath of a living being. A quiet whisper came from behind the translucent staircase and blue flashes crept along the walls. Olive looked at Frank with wide-open eyes, her heart pounding like a hammer. The mysterious light seemed to invite them in... and then they heard someone's voice - very quiet, but clearly calling them by name. At that moment they both held their breath. Should they go inside?