Basia and Franek were best friends. They spent every Saturday together in the old park, where huge chestnut trees grew and woodpeckers clucked. One day, when the sun was shining exceptionally hard, the children noticed something unusual: just behind a currant bush, a narrow path appeared that had never been there before. Intrigued, they stepped onto the Luminous Alley. On each pebble of the path, different colours shimmered: yellow for joy, blue for peace, red for anger and green for jealousy. As Basia jumped from pebble to pebble and laughed loudly, the stones glowed yellow. Franek, who was a little frightened, could see the pebbles below him glowing a light purple. "Look, these colours change when we feel something different!" - exclaimed Basia. "It must be some kind of enchanted place!" Frank felt a thrill of excitement. Suddenly, a new stone appeared just at the fork in the path. It shimmered with a grey-silver glow that none of them had ever seen. The children stopped, looking on in disbelief. Franek felt a tightening in his stomach and Basia suddenly became very quiet. There was silence all around, as if the whole avenue had held its breath. What would happen if they stood together on this new grey-silver stone?