Some info and a short description of this South Park episode on South Park Zone:
South Park - Child Abduction Is Not Funny" is episode 90 of the Comedy Central series South Park. It originally aired on July 24, 2002. This episode mocks moral panics, and was the last to feature Tweek as the "fourth friend" alongside Stan, Kyle and Cartman.
The parents hire Tuong Lu Kim to build a wall around the city to protect the children from kidnappers, but end up letting their kids go after learning that parents are more likely to abduct their own children than total strangers.
Tuong Lu Kim continues the historical war between Chinese and Mongolians.
The South Park people realize that they overreacted to the news stories, and that to cut themselves off from the rest of the world with the wall denies new possibilities.
South Park Spoiler Alert!
(The complete plot for this South Park Episode)
With the media full of school shootings, terrorist threats, and child abductions, the parents of South Park grow concerned about the safety of their children. Tweek is scared the most by the media reports, and his parents serve only to exacerbate his fears by turning their house into a virtual prison and conducting random drills.Tweak loses his ability to empathise with others and refuses to assist a cripple on train tracks. After a real child abductor (pretending to be the ghost of human kindness) fails to kidnap Tweek, the parents of South Park are put on high alert.
Now the parents are on high alert. They buy grotesque helmet-like devices for their children named "Child Tracker" and have the owner of City Wok, Mr. Lu Kim build a huge wall around the city similar to the Great Wall of China. Mr. Kim is offended for them thinking that just because he is Chinese that he can build an enormous wall around the town single-handedly, but after an impassioned speech by Randy, Mr. Kim reluctantly agrees and 'does' build the wall. He is almost finished when a band of Mongols appear out of nowhere and attack the wall for no apparent reason. Mr. Kim drives them off by throwing bricks, then proceeds to finish the wall. The Mongols soon return, but when Mr. Kim arrives to drive them off, he finds only their hats and cloaks propped up on branches and a tape recorder playing battle sounds; the real Mongols are back where Kim was before. They break off their attack, but only after putting a large hole in the wall.
Meanwhile, back within the town a news report states that the parents are most likely to abduct their own children (which is true even in real life, as most child abductions occur as the result of a custody battle). Blindly believing what they have been told, they send their children from the city in a tearful ceremony in order to avoid putting their children in danger of being kidnapped by their own parents. As they leave, the children wonder about how stupid their parents are sometimes.
Within the week, the children join forces with the Mongols, having apparently learned their language, and enraged at the irresponsible thinking their parents have exhibited. The Mongols then move on the wall again, where Mr. Kim is dressed for battle. He then does his "war dance", but while he is doing this, the children wheel a large cart laden with explosives in behind him and blow up the wall. The parents arrive to investigate the explosion, and are reunited with their kids, although the parents believe their children have forgotten them in the short space of four days. They realize that they overreacted to the news stories, and that to cut themselves off from the rest of the world with the wall denies new possibilities. Mayor McDaniels orders Mr. Lu Kim to "tear down this wall," angering him once more.