Evan Wistlepants had chased eleven rainbows, and he had caught zero. He knew the gold was real. His grandfather swore a pot waited where each rainbow touched the ground. But the ground was a lie. Every time Evan ran toward a rainbow, it slid sideways across the hills. He stumbled through bogs and bramble, always arriving where the colors had just been. Today a fresh rainbow arched over the valley, and Evan stood at its base, breathing hard, with no idea which hill hid its foot. He sat on a wet rock and pulled out his grandfather's old map. It showed nothing useful. Rainbows did not stay still for maps. Evan needed a way to fix the foot in place, to point at it and know. Otherwise he would run blind until his legs gave out. Across the water, a castle of glass and dark stone caught the light. The glass walls threw the rainbow back at him, doubled and bright. Evan sat up. The reflection did not slide. It held steady on the water below the castle, where two white swans drifted close, their necks curved toward each other. The colors landed right between them. Evan understood. He could not track the rainbow in the sky. But the glass walls copied it, and the still water held the copy. If he lined up the castle's reflection with the real arch, the two lines would cross. Where they crossed was the true foot. He found a trailing willow at the water's edge. Its long branches hung like ropes. Evan climbed into the lower limbs and steadied himself. From there he sighted along the real rainbow with one eye. Then he turned and sighted the reflection in the glass walls. He held both lines in his mind and followed them down. They met at a low green hill past the swans. Not where the colors seemed to touch. A full field away. Evan climbed down and ran, but this time he did not chase the colors. He kept his eyes on the hill his two lines had marked. The rainbow slid, as it always did. The hill did not. He reached the crest and stopped. There was no pot. There was a hole in the ground, round and clean, exactly the width of a pot. The grass around it was pressed flat in a ring. Something heavy had rested here, and recently. Fresh drag marks led away down the far slope, two deep grooves in the mud. Evan knelt and touched the empty ring. His trick worked. He could find where a rainbow truly landed. But the gold had already been taken, and whoever took it was dragging it somewhere ahead of him. He stood and looked at the drag marks. For the first time, the chase had a direction.