Franek and Lena find a hidden door beneath an ancient oak tree in the forest, and step into a strange underground world that seems to be waiting for them.
Franek loved the woods in summer, when sunlight sifted through the leaves and the air smelled of pine sap, warm earth, and something wild just out of sight. Lena usually stayed home with her books, but that morning she had followed him anyway, quiet and curious, as if the forest had called her too.
Their favourite place was the old oak on the hill. Its trunk was so broad that even with arms stretched wide, the two of them could not have circled it. The roots rose from the ground like frozen waves, tangled in moss and fallen leaves.
Franek was the first to notice the glint. Something round and dark peeked from between the roots. He knelt, brushed away the moss, and found the broken edge of a metal doorknob.
Lena came closer. Together they scraped at the earth with their hands until the ground gave way in a shallow sigh. A small door appeared beneath the oak, no taller than Franek’s shoulder, hidden so well it looked as if the tree had grown around it. Strange carvings curled across the wood: feathered shapes, scaled tails, narrow eyes that seemed to follow them. In the centre, a blue stone caught the light and shimmered like water.
Lena drew back. "Maybe we should leave it."
Franek swallowed, but his hand was already on the knob. "We have to see what’s inside."
The door opened at once.
Cold air touched their faces. Beyond it lay a tunnel lit by a pale silver glow, as if moonlight had been trapped underground. The smell that drifted out was unfamiliar, half vanilla and half smoke, like something burned long ago and never quite gone.
Lena took Franek’s hand, and they stepped inside.
The tunnel widened with every pace, until it opened into a vast cave that stole Franek’s breath. Crystals burned softly in the stone walls. Tiny lights fluttered overhead like flying sparks. Far below, a lake shimmered in impossible colours, red and gold and blue all at once. Over its surface moved shadows with wings and tails, silent and graceful, nothing like anything in any book Lena had ever read.
Then a voice echoed from above the lake.
"What are you doing here, human children?"
Franek and Lena froze.
The water near the far shore rippled. Something there had begun to move.