The first day of the summer holidays smelled of strawberries and freshly cut grass. The sun was playing hide-and-seek between the leaves and the wind whispered in the woods just beyond the Birch Valley meadow. Pola had a leather rucksack in her lap and Cuba held a bark boat under his arm. Their dog, Mig, was wagging his tail so hard that dewdrops were leaping from the grass. - 'We're just going to the stream and the meadow,' called out Pola to her mother, who was watering the tomatoes. - Stay close to the Old Oak and be together - replied mum. - Come back before afternoon. - Hau! - added Mig, as if promising to keep watch. The stream purred softly and glistened like a silver ribbon. Cuba put the boat on the water. It floated, swaying gently, until suddenly it snagged on something bright that was stuck under the roots of a willow tree. - Look! The jar! - shouted Kuba. Pola crouched down and carefully pulled out the jar. Inside, behind the glass, she could see a rolled piece of paper tied with blue thread. Mig sniffed the glass and sneezed. - Pussycat," laughed Pola. - I'll open it. The glass was cool and the lid slightly rusty, but it finally let go. Pola slid out a wad and unrolled it in her lap. On the sheet someone had drawn a thick tree trunk with a round circle in the middle, next to it a red bridge over a stream and a path made up of small dots. At the end of the dots was a big, wavy X like a kiss. - This looks like our meadow! - whispered Cuba. - And the Old Oak! The one on the hill! There was also a paw painted on the corner of the card, almost like a mud stamp. Mig looked at his downy claw as if to say, "That's mine!" - Who could have drawn that? - wondered Pola. She moved her finger over the dots. - They lead from the bridge to the oak tree. - Let's go! - asked Kuba. - Just to the oak tree, just like mum said. Packing took only a moment. Pola put two apples, a bottle of water and a whistle in her backpack. Kuba put away a magnifying glass and a small compass with a plastic needle that he got in kindergarten. Mig got a handkerchief with peas on it because it suited his mouth so well. They crossed the red bridge. The planks squeaked and the stream flashed sunlight from under the saucer of wood. Beyond the bridge a meadow began. Chamomiles hugged the grasses and dragonflies drew blue figure eights in the air. - See! - Pola pointed to a row of daisies. The flowers were arranged in a delicate arrow, exactly like dots on a piece of paper. - As if someone had scattered footprints. They walked slowly, step by step, so as not to miss anything. Mig ran from scent to scent, but always returned when Pola whistled. Somewhere high up, a woodpecker was tapping out its rhythm, and from far away a soft sound could be heard: dzyń... dzyń... like a tiny bell. - Do you hear it? - asked Kuba, stopping. - Where is it coming from? - Maybe from the wind - answered Pola, although she herself was already looking towards the hill with the Old Oak. The Old Oak grew out of the grass like a gentle tower. Its bark was wrinkled like a map of rivers, and its boughs spread a shade cool and fragrant with summer. In the midday light, the trunk shimmered with warmth and the leaves spoke shu... shu... like a lullaby. - Look at this place - Pola put a piece of paper on her lap and compared the drawing with the tree. - There should be a circle here... She moved her hand over the bark and felt a smooth disc, soft like a polished walnut. It wasn't big, about the size of a sandwich plate. Mig sat down opposite and tilted his head. - 'This looks like...', Cuba began, but didn't finish because a speck of light shimmered on the smooth disc. The sun, which was squeezing through the leaves, went straight into the centre of the circle. Ding... ding... it sounded clearer, although no one could see from where. Pola held her breath. The disc suddenly vibrated under her fingers, as if muttering contentedly. A thin line appeared on the edge, first like a scratch, then like a real outline. The bark around it moved silently, and the disc turned into the outline of a tiny door. - Oh my... - whispered Cuba. - They... - Shh - said Pola. - Listen. Behind the door something rustled softly, like pages in a book or wings. Mig raised his paw and touched the bark. At the same moment, a very soft, warm breeze flowed from inside the trunk, which smelled of honey and lime. Pola looked at Kuba. - Are you ready? Kuba nodded. He moved the compass over the wheel, as if that would help. The needle twitched and twirled, and the bell sounded again: ding... and ding. Field touched the spot where the dash had appeared. The bark was as warm as a heated pebble. At the very centre of the door, where there had previously been only smoothness, something round and golden emerged. A small, shiny button, like a lump from an old coat. It made a 'click' and paused, waiting. - 'I'm trying,' whispered Pola. Her heart tapped twice, once fast, once hard. Kuba squeezed the hem of her rucksack. Mig laid his tail on the grass and didn't even wiggle. Pola's fingers embraced the button. It was warm and smooth. The air stagnated, as if the whole day had held its breath with them. Somewhere high up a woodpecker stopped tapping. A drop of dew fell from a leaf and crashed silently. Then the door vibrated, for a fraction of a moment it swung open, and something unusually bright twinkled in the crack, like a star locked in a pocket