In order to save their family workshop from foreclosure, the younger brother suggests to his brainless older brother that Lupin may be the answer to their financial problem. They build a smart safe for the Greater Tokyo Bank which can only opened by someone with no brainpower, as a special challenge to Lupin, the world's greatest thief. Stung by the resilience of this obstacle, Jigen, Fujiko and Goemon begin to implement a sadistic sleep deprivation, beating and exercise regime to kill off Lupin's brain cells. However, at the publicized event of the safe's opening, Lupin instead consumes lots of blueback fish, boosting his brains so that the safe's IQ counter is overloaded and resets itself, thus opening the safe. While the contest ends in a draw, the brothers become celebrities and begin selling canned fish, recovering their property.