Supposedly, an old man named Genhardt, who used to work for Hitler, knows the secret of the legacy of Hitler and is living on the other side of the Berlin Wall. After getting the old man across the Berlin Wall from East to West Germany, Lupin is unable to get the man to recall the location of the legacy. Lupin and the others plan a reenactment of the days of Hitler in order to get Genhardt to reveal the location of Hitler's Legacy.

Zenigata has been suffering from a persecution complex, one in which he feels certain Lupin is watching him. He seeks the help of psychiatrists to get rid of his delusions of Lupin. Meanwhile, some group has implanted microfilm containing a process developed by NASA for creating artificial diamond in one of Zenigata's back teeth. Lupin goes up against that group and attempts to take the microfilm for himself.

Setting his sights on the large medallion on Generalissimo Hutler's chest, which contains a 50-carat ruby, Lupin should have been able to take it easily enough, using his special rod-and-reel technique, but ends up exposing the Generalissimo's secret toupee instead when the wind blows the hook on his fishing line over Hutler's head instead of the jewel. The infuriated Hutler orders that Lupin and company be wiped out, and in the face of the attack by his combined armed forces, a wounded Lupin makes his stand in an old castle with Fujiko while Jigen and Goemon attempt to save them.

Lupin and Jigen hear of an amazing treasure in a remote area, and go after it. Upon saving a woman being attacked by ruffians, the place she leads them to, by way of thanks, is a paradise on earth, with good-looking women everywhere. Lupin accepts the thanks, completely forgetting about the treasure. The fact is, this mansion full of women is for the purpose of seducing men, and then exposing them to an aging gas. Zenigata falls for the same trick as well, and he ends up inside the mansion alongside Lupin. Jigen gives up on trying to get Lupin's mind back on the treasure and leaves, but then realizes the secret of the mansion and enlists Goemon's help in saving Lupin. Meanwhile, Fujiko, who is also after the treasure of the mansion, ends up trapped inside, as well.

Lupin is feeling out of sorts, because lately he hasn't been able to get a hold of Fujiko. When he receives a phone call saying that she'll marry him if he passes her test, he takes off, but what he finds waiting for him is Fujiko's aunt, Mine Bujiko. The test is, either find Rommel's Gold, or pay for failing to do so with his life. Lupin throws himself into deciphering ancient hieroglyphics and almost gives up, but Fujiko's holographic image keeps him going. After unlocking the secret of the hieroglyphics, Lupin discovers that Bujiko is actually Fujiko in disguise.

Zenigata heads to Spain after learning that Lupin is there. Meanwhile, Lupin and Jigen are in a Barcelona bar where a dancer catches the eye of Jigen. The woman works for Meyer, who, having been beaten by Lupin a number of times, sets Lupin and Jigen up to kill each other off by of making them appear to be enemies in disguise to one another. Lupin and Jigen meet up for a shooting match in the dark, but a secret code between them that involves shots aimed at a coin alerts Lupin and Jigen to the fact that they're being tricked.