In this installment of Dragon Ball Z, Dr. Kochin, a celebrated expert in biotechnology, collects the Dragon Balls within his laboratory to free his mentor, Dr. Uirou—a deranged scientist aiming for world domination—who has been sealed in the eternal ice of the Tsurumai-Tsuburi Mountains. While Son Gohan and Oolong search for the Dragon Balls, they fall into a trap set by Dr. Kochin's creations, called Bio-Men. Piccolo, nearby, tries to rescue Gohan and Oolong but is interrupted by three mysterious fighters. The fight is cut short when the ice below collapses, burying Gohan and Oolong.
After waking up, they return to Kame House, where they are again confronted by Bio-Men demanding that Muten Roshi join them. Roshi refuses and quickly defeats the attackers, drawing Dr. Kochin's attention. Convinced that Muten Roshi is the strongest fighter in the world, Dr. Kochin kidnaps Bulma to force Roshi into participating in his hidden plan to release his master. The mystery grows: who exactly are Dr. Kochin and Dr. Uirou, and what sinister schemes do they have in store?