'''Operation Great Wall of China Invader''' [[note]]万里の長城インベーダー作戦 (''Banri no Choojoo Invader Sakusen'')[[/note]], also released in English as "Operation INVADER at the Great Wall of China". Original air date of July 23, 1979.

Lupin and his gang infiltrate an ancient temple in Peking, looking for an ancient and priceless set of Mahjong hidden there. However, this time not only Zenigata is after them, but also a dangerous band of Chinese criminals lead by the villainous Hou Chang is on their heels, looking for the precious tiles. Taking advantage of Peking’s traffic, the heroes manage to evade their attackers at first, but when they’re cornered a second time by the Chinese gang, a mysterious girl comes to their rescue in a car. Back to safety, the girl shows something highly unusual by spilling a strange potion over a book, drinking it and being able to speak Japanese flawlessly (except for the strong Kansai accent), much to Lupin’s surprise: she then explains that the liquid she employed is a secret medicine which can be used to absorb the contents of a book and learn them completely, which is how she was able to speak Japanese in a jiff. She then offers the learning serum to our heroes before leaving.

Later on, that day, Lupin and his friends are playing with the precious Mahjong set when Fujiko claims that Lupin should try to learn to be more wise and behaved, so the thief half-jokingly decides to use the learning serum with Confucius’ works to increase his wits, but much to everyone’s surprise he suddenly screams angrily at Fujiko to leave after drinking the potion and feel repulsed by the money. Jigen and Goemon realize that he’s behaving like a Confucian Sage, and a cackle confirms their suspects: the girl from before appear on television and reveals that she’s Hou Chang in disguise and that that potion is a secret invention of his, and makes whoever drinks it change its mannerism according to the book in contact with the medicine, and also that he used this potion diluted in the water system to cause the Communist Revolution and Mao’s uprising. The criminal gloats that now that Lupin has become a Sage it should be easy for them to manipulate him into doing their bidding, and in fact the Sage Lupin not only is disgusted by Fujiko’s presence, but is also ashamed to be in the company of thieves and decides to give the Mahjong set back to its rightful owner, departing from the hideout as his amazed former friends look on.

Back at the temple, Hou Chang and his men stumbles into Lupin and manage to gain his trust, but they discover that the precious imperial tiles are missing from the Mahjong box, and Lupin seemingly has forgotten their location, so the boss decides to stick with the Sage a little more to find out where are the tiles. While all this happens, Zenigata is trying to discover the whereabouts of Lupin and his gang asking the help of Peking’s population, and learns that they have been spotted somewhere near the Great Wall. It turns out that Hou Chang’s hideout is there in one of the keeps of the Wall, where he’s taking Sage Lupin, who still doesn’t remember where did he put the tiles. As they drive on the wall they’re chased by Zenigata, but Hou Chang gives Lupin his special weapon, a gun that shoots the learning serum, and using a classic Japanese book (“I am a Cat”) hits Zenigata in the mouth, making him act like a cat. In Hou Chang’s hideout, Lupin is still forgetful, but suggest that a good meal may restore his memory and so the gangster and his underlings are forced to cook a delicious meal for the “sage”, who’s taking a sneaky look at Hou Chang’s collection of stolen goods in another room. Hou Chang is starting to doubt Lupin’s current amnesia, so as soon as he learns that Lupin’s gang tried to sneak in the hideout but were caught, he decides to test Lupin’s brainwashing and brings him in the same room as his friends, whom he starts to threaten. The sage seems unconcerned with their fate, no matter if he’s torturing Jigen or harassing Fujiko, but as soon as Hou Chang is distracted Lupin hits him on the head with a pot, taking him out of commission.

Turns out that Lupin never trusted that suspicious draught, so he hid a book his grandfather wrote in Confucius’ work, negating the effect of the potion. In no time, the group neutralize the henchmen and makes off with most of the treasure, but are confronted by Hou Chang, who demands to know where Lupin hid the tiles; Lupin reveals a hidden compartment in the box and with a trick manages to steal Hou Chang’s special gun and flee by car on the Great Wall. However, the gang boss reveals his trump card: his base is actually a wheeled ironclad armed with guns and able to run on the Great Wall thanks to his cog-like wheels. With this machinery, soon Lupin and his gang find themselves on the wrong end of an Invader-like game and eventually the car is shot, forcing them to flee on foot. Goemon slices part of the wall’s top, causing the base to crash, and as Hou Chang tries to shoot them one last time Jigen squirts the learning serum in his mouth after putting a book about babies in the tank; as a result, Hou Chang now acts as a harmless baby and Lupin decides to let him be. The group recovers another car but are soon confronted by Zenigata, who still believes to be a cat, and after some hesitation, the thief decide to cure him from his ailment, which of course means that once again everything’s back to normal and our heroes are still on the run.

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!!'''This episode contains examples of:'''

* BeenThereShapedHistory: Chang claims responsability for the Maoist revolution, having tainted the water supplies with his learning serum.
* CrazyPrepared: Not only Lupin hid the Mahjong tiles in its very container, but he also took precautions to fake the effects of the learning serum.
* FacePalm: Sage!Lupin does this when he learns that his comrades are thieves.
* HeManWomanHater: Sage!Lupin refuses to stay in the same room as Fujiko, to the point of poking her away with a broom.
* HoistByHisOwnPetard: Chang ends up receiving a literal taste of his own medicine.
* LatexPerfection: Hou Chang as the pretty chinese girl.
* MonumentalDamage: In the climax, part of the Great Wall are greatly damaged.
* ShoutOut: To the ''Invader'' videogame, right there in the title!