Lila was seven and had a pocket full of buttons that pretended to be planets. Olek was five and always carried a torch, even though it was daytime. Piko was a robot dog with a blue nose and a soft light in his belly. He could only say 'pip' and 'chip', but Lila and Olek understood him like a best friend. That evening, the sky was as clear as glass and the stars were so sharp that it seemed as if they could be picked up with a spoon. In the window of Lila and Olek's room lay a large, soft blanket. It had silver threads that glittered even when the light was off. It was a Rocket Blanket, a gift from Aunt Hela, who claimed that some blankets could do more than warm the knees. - 'Look,' whispered Lila, putting her nose to the glass. - This star is flashing differently. - Three, two, three... - counted Olek, shining his torch at the ceiling as if he were making a map on it. - Pip? - added Piko and moved his ears. The star blinked again: three times, pause, two times, pause, three times. As if it was saying: "Hello! Hey! Here!" Lila felt the silver threads of the blanket tremble slightly under her fingers. - It's a signal - she whispered. - The blanket-rocket already knows. When Lila and Olek jumped under the Blanket-Rocket, the air became cool and smelled like the night after the rain. Piko lay down on their feet and muttered "chip-chip". Lila touched the silver piping and said what she always said when it was time to fly: - Silver up, buttons to the stars! The rocket blanket tightened like a sail. The room became very quiet for a second, and then the window widened into a wide, soft tunnel of clouds and sparks. The children were pulled inside together with Piko. They were flying! They passed the neighbours' balcony, glided past the moon, which looked like a smiling bun, and then sailed onwards to where the air becomes a light whisper and the stars are as close as the lights on a Christmas tree. - Pip! - Piko stuck out his nose and blinked in rhythm: three, two, three. - Direction: purple moon - decided Lila, because that's where it blinked the most. This was not the big, familiar moon. This one was tiny, round like a plum and the colour of blackcurrant juice. There were silver crumbs circling around it, as if someone had scattered glitter. The blanket-rocket sat soft as a feather on its surface. Dust crunched underfoot, but did not soil his shoes. He smelled a hint of vanilla and something fresh, like morning. The sky above them was dark and very still, only there, by the rocks, something flashed in rhythm: three, two, three. - 'Don't go far,' Lila said to Olek, although she herself wanted to run first. Olek squeezed her hand so that she felt the warmth up to her elbow. Piko trotted up beside her, leaving little heart-shaped footprints in the dust. They approached a smooth rock wall. It was high and dark, smooth as a mirror. It had no cracks or crevices, only at the height of their knees they saw three gouged stars: one next to the other. Above them was another, and then another - five in total, but arranged in groups: three, break, two, break, three. - Oh dear - sighed Olek. - It's like flashing that star. - Pip-pip-pip... chip-chip... pip-pip-pip - played Piko, touching the first three stars with his nose, then two, and then three again. The scale trembled, very gently, as if it was waking up. A noise came from inside, quiet, reminiscent of breathing. Lila felt a tickle in her fingers. Olek put the torch in his pocket and looked around. Above them circled a tiny skylight in a suit of dust. No, it wasn't a skylight. It was a tiny crumb of ice that reflected their own lights. - 'There's someone here,' Olek said in a half-hearted voice. - 'Or something is calling us,' added Lila just as quietly. Piko squatted down on the gouged stars and once again played the rhythm. This time his nose blushed harder and his tummy lit up like a little moon inside. The scale responded: first one, then two, and finally three quiet taps from deep within. - Did you hear that? - Lila squeezed Olek's hand again. - I heard it - he nodded. - It's like knock-knock... pu-kuk... knock-knock. The ground beneath their feet twitched, but only a little, as if the purple moon had taken a small, very polite step. The stars in the rock glowed with soft light. The lines between them flowed like milky trickles and began to draw the delicate shape of a door on the wall. No handle, no lock. A door that knows by itself when it is ready. - If it opens... - Lila started, but didn't finish, because she had a question full in one thought. - 'If they open, we'll all go in together,' said Olek very seriously and shook Piko's paw as one would shake the hand of an important guest. Piko 'piped' quietly, as if nodding. His blue nose trembled, and inside, streaks of light danced like tiny fish in a jar of water. A thin shadow flew across the purple sky - maybe a pebble, maybe a dust bird - and disappeared as quickly as it had appeared. Then the door in the rock moved. First in a way that no one but Piko would have noticed. Then more clearly: the line in the middle widened by a hair, by two, by the shadow of a finger. A thin line of light dripped from inside, very white and very still. It smelled like a new book and like a garden after a storm. - Can you hear? - Lila asked. - There it is... She didn't finish because another sound came from behind the door, this time soft, like laughter that is still ashamed. Three notes, pause, two, pause, three. Then something on the other side moved closer, so close that the light danced on Piko's nose and a shadow moved across Olek's shoes. The door vibrated harder, drew a thin, luminous stripe in the dust, and began to move a little further apart, when just inside the threshold a shape flashed by....