Mungo Baobab and his droids, Threepio and Artoo, are trailing the Rainbow comets of Manda in search of the fabled Roon system. Before they get there, they make an enemy out of the greedy Governor Koong. On Roon, they meet Auren Yomm and join her Umbo racing team in the Roon Games. Mungo takes up his old uncle Ogger's quest of finding the source of the valuable Roonstones. Meanwhile, Koong uses germ warfare against the rebellious province of Umboo and it becomes a race against time to find a cure for the Rooze infection.