C-3PO and R2-D2 are on their way to Biitu to meet their new master, Mungo Baobab, when their ship is attacked and they are taken prisoner. Biitu has been taken over by the giant mechanical Great Heep who works with the Empire, enslaving the natives by using droid enforcers and draining R2 units to keep up his strength. Meanwhile Mungo has been imprisoned to be handed over to his arch enemy Admiral Screed.