In the space year 1422 (6216 in the Master System version), the Fantasy Zone was cast in panic at the collapse of the interplanetary monetary system. The Space Guild brings to light the plans of the planet Menon, whose forces are stealing the other planets' currencies to fund a huge fortress in the Fantasy Zone. Opa-Opa is sent to stop the invading army and discover who is behind it. In the end, it turns out that the leader was none other than Opa-Opa's long lost father, a revelation that leaves Opa-Opa with mixed emotions.