Scylla the witch is back again, and this time she has in her possession the formula for supreme evil. She needs the rare black diamonds for her formula - and they are only to be found on Jungle Island where the Kikurians live. With Don Croco's help, she has captured all the wretched Kikurians and forced them to toil in the mines, day and night.

Hugo must free all the captured Kikurians and stop the production of Scylla's evil potion.