After a long rainy spell, large stretches of the prairie are flooded, much to the displeasure of most of its inhabitants. Yakari visits his friends to make sure everyone is alright, then falls asleep that night and dreams of clouds mysteriously coming out of the water. The young Sioux's dreams are not always completely random, though, and the next day he rides out in search of signs. What he finds will soon unite all his friends in a desperate rescue mission ...