The episode starts at an old, abandoned apartment building. A man named Bob is knocking the structure down with the wrecking ball, and expresses his feelings for his work. While Bob works, a bluish-skinned looking man in ragged clothes named Clancy steps out of one of the holes made by the ball. Insects swarm all over his body, and it seems that he doesn't mind. He talks, and says that the bugs are a part of him. Joe, Bob's boss, notices what Clancy said, and ordered Bob to stop his work. Clancy tells the workers to leave immediately. Bob replies with a chuckle to his statement, and tells Clancy that the building must be torn down by the order of Councilwoman Liang. Joe agrees with Bob, and tells Clancy that the place must come down, whether he rejects it or not. Clancy is infuriated and releases a swarm of wasps from his sleeves. The bugs chase down Bob and they lift him up to Clancy. Bob tells him to put him down, but Clancy replies with a threat if they continue what they are doing.
In another part of the city, a criminal is speeding through the streets riding a hot rod, confident that he won't be caught. In the RV, Gwen spots someone and goes to tell Grandpa Max. He wants to know she is sure. She replies with a yes, and Upgrade passed by merged with a motorcycle. The criminal cuts through the traffic, and Upgrade decides to take a different route by driving on the sidewalk. He tells the people to give him way. During his chase, a car-transporting semi cuts Ben off, though he gets by, by using the back of the truck as a ramp. The criminal notices Ben closing in, and he speeds up. An RV moves into the street intersection once the street light changed, and Upgrade tips on his side to avoid a crash. He eventually catches up again with the criminal, and uses his eye positronic blaster to blow up the criminal's trunk, and all the money he stole goes into the air. Ben comments that people just can't hold onto their cash. Upgrade then creates spikes on his wheel and rams hard into the tire of the criminal's car, and he crashes. Upgrade drives next to the criminal and notices that no one is driving it, and he can't believe what just happened. Upgrade then burs rubber onto the criminal's face and the police shows up, at the point where Ben leaves. He goes around the corner, and spots a nearby ice cream truck. He stopped a bad guy, and he feels that it is OK to take a small treat. Upgrade separates from the motorcycle and climbs into the back of the truck.
The criminal is trying to explain to what he just saw to the police. They don't believe his story about a driverless motorcycle, of course. Meanwhile, Grandpa Max and Gwen are looking for Ben. Gwen eventually finds the odd-shaped motorcycle nearby and ice cream truck, and assumes that Ben is somewhere around there. They find Ben inside the truck, in his human form, shivering and his skin is pale. He also has a runny nose. Grandpa Max asks Ben if he is OK, and replies with a sneeze. Grandpa Max takes it as a no.
In the RV, Grandpa Max takes Ben's temperature. The thermometer reads 101, and Grandpa Max confirms that he has a summer cold. Gwen makes fun of his condition, stating that he should think before he acts. Ben sneezes, and decides to use Gwen's new blouse as a rag. She complains, and Ben in return tells her what she just told him. Gwen then pulls out various medical supplies, including a hospital mask. Ben however says that he doesn't need any of it. Gwen states that Ben is now a bug who tends to spread to everyone. He then replies if he can just remain inside a closet until he feels better. Gwen agrees with him. But Grandpa Max says that he just needs some medicine. Grandpa Max decides to give Ben a dose of his famous San Ju Yen Pien cold medication, and they head out to Chinatown to acquire the needed ingredients.
In Chinatown, celebration is occurring. A dragon dance is taking place and a parade of people in costumes. Ben, Gwen, and Grandpa Max leave a drug store just after the parade passes. Grandpa Max, however, is unhappy for not being able to find fresh potaigadon root, since it is now freeze dried at these days. Ben instead insists for a milkshake for his sore throat. Grandpa Max, however, says that the stinkweed honey in the San Ju Yen Pien will do the trick. He takes a whiff of the medicine, and it was repulsive. Gwen then asks Grandpa Max where he learned the recipe for the medication. He answers her question by saying that he learned the recipe from Guangdong, China. Gwen however gives him a blank stare, and Grandpa Max says that there is plumbing in China, too.
On a nearby platform, Councilwoman Liang is thanking everyone in a crowd of people for their support of her redevelopment program. She says that it's a dream come true. Her speech is interrupted by a swarm of wasps, and they scare off the crowd. Clancy then flies up, riding on a cloud of wasps, and he will make her dreams a nightmare. The wasps continue to chase everyone as they talk. Clancy then says he won't allow anyone to tear down his and his companion's apartment. Liang calls him as the nut job that wouldn't leave, however he's glad to make an impression. He orders his wasps to pick her up, and he says that she is bringing her home for dinner – she'll be the main course.
In another part of the city, Ben decides to deal with the bugs. He prepares his Omnitrix, and transforms into Wildmutt. His cold has appeared to also spread with his alien form. Wildmutt's nostrils were clogged with lots of mucus. He is unable to track his surroundings, and runs about aimlessly, without regard to bumping on things. Gwen wonders for Ben's strange behavior. Grandpa Max, however, knows what is going on, and explains it to Gwen. So she decides to be the guide for him, however it doesn't work well. Her directions only lead her to be thrown into a fireworks stand, and end up being trapped by stacks of boxes. It also knocks down one of the paper Chinese lamps on a nearby stand, starting a fire near the fireworks. Grandpa Max was able to step in to save her, by tipping a cart full of chicken dumplings into the flames. Gwen thanks him for the save, but hopes that she doesn't mind smelling like dumplings for a while. As Wildmutt continues to run without caution, he has a trash can on his head, and crashes into another obstacle.
In the RV, Ben feels unhappy of what happened as Wildmutt. He thinks that it is just making things even worse. Grandpa Max then hands him some more of the medication. Ben smells it, again repulsed by it. It smells worse than it tastes, but it just may be the other way around. But Grandpa Max needs to worry more that the virus also affects his alien forms. Ben then drinks the medicine, and is not happy about the taste. Grandpa Max states that he should get used to it after several doses. Gwen then comes up with some important info about Clancy, and found that the apartment is his only residence, which is scheduled to be demolished. Ben uses the distraction to hide the medicine Grandpa Max gave him so he won't take anymore. Gwen then says that he lives at 8610 Chester Street.
Inside Clancy's apartment, Councilwoman Liang is covered in spiders. She pleads to Clancy to have mercy on her. Clancy says that the spiders are black widows, and tells her not to make sudden movements. He then tells her the reason why she should not destroy the building. He says that his grandfather built the building, and that he and his insects grew up here. He says that they are the only ones who understand, and no one should evict them.
Ben, Gwen, and Grandpa Max then arrive at the building in the RV. Gwen says that the place is nice to visit, yet the building is not nice to live in. Grandpa Max tells her and Ben to stay together. They head inside, and the place is falling apart, and insects are crawling through the rafters. Grandpa Max then finds an article on the wall. It reads "BUGS SURVIVE NUCLEAR BLAST" and has appropriate pictures. Gwen finds an insect nest and says that they are near. Grandpa Max then notices that Ben is gone and wonders where he has gone again. They start looking, but a large shadow covers them. A large figure with four eyes and horns approach them. They then find out that it's Four Arms, yet again to pull a prank on Gwen. But his appearance was paler, which says that he is suffering from the virus also. Four Arms laughs at his own joke, and they hear screaming from the floor above. Four Arms picks up Gwen and Grandpa Max and prepares to jump through the ceiling. When they do, they notice that he has hives on his underarms, yet mutated on him, becoming large in appearance and pungent, which Gwen states. He then jumps to the next floor.
They find the Councilwoman still covered in spiders. She tells them to stop since the spiders are black widows. Four Arms inadvertently takes care of the black widows when he sneezes, which covers Liang in green mucus, while washing the spiders away at the same time. Despite the nature of the rescue, she thanks Ben for helping her. Clancy then shows up, and tells them that they are trespassing. He then orders an army of ants to deal with them. They form a fist and punch Four Arms. Clancy then states that he they'll rule mankind. The ants regroup and attack Grandpa Max. He then was able to dodge them. At the same time, the termites devour the floor beneath Gwen, and leave her hanging on from a ledge. Liang was able to save her. Meanwhile, Four Arms gets back up on his feet, and attempts to attack Clancy. He rallies his ants again and they swarm on Four Arms. He scratches wildly at them, and knocks over many of the building's support beams. Clancy yells at him for this, but he doesn't listen. Clancy then summons a swarm of wasps to protect him from the collapsing building. As Four Arms continue to deal with the ants, Gwen immediately comments on the collapsing building. Liang says that they should escape immediately, but time has run out, and collapses on top of them.
The building collapses completely, and Four Arms lifts up a rather large slab of concrete, shielding the others from the collapse. Clancy was also in the rubble, covered with cockroaches. The cockroaches died protecting him, which infuriated him. He then plans to exterminate the whole city. He calls out a humongous swarm of wasps to pick him up, and Liang comments on the day she's had. Gwen answers that they have been on the same situations. Liang then wonders where Four Arms went, and wanted to thank him for saving her. Ben says that he'll let him know. Grandpa Max asks if she can find her way back home, and answers yes. She leaves, and leaves Ben up to thinking where Clancy has gone to. Grandpa Max looks around, and spots the local nuclear plant. He immediately concludes where Clancy went, since a nuclear blast would be the only way to destroy the entire city.
On the way to the nuclear plant, Ben is shivering in the RV. He asks Grandpa Max to turn the heat on, though it is already. Grandpa Max tells Gwen to give Ben some of the San Ju Yen Pien for Ben to drink. Ben would rather not drink it, so he lies about taking a dose already. Gwen then found some information of insects, and she repeats the info aloud, yet Ben just wants to know just how to kill them. She says that short of an ice age, or a tanker full of pesticide, yet barbecuing them would be the best solution. Ben says that he knows just the chef to do it.
They arrive at the nuclear plant, and searched around for Clancy. The lights go off for a moment, and it comes back on, followed by an alarm. Ben wonders if it's bad, yet it clearly is. A voice confirms that the reactor's core is rising rapidly and nearing critical status. They run to the control room, only to find the controls destroyed. Grandpa Max says that the only way is to shut it down manually. He says that there should be an emergency override system inside the reactor core. Gwen ponders if Grandpa Max learned this from a monk in China too. A cockroach then crawls near Gwen and she jumps away. Clancy then reveals himself in the room, making a joke about them wanting a front row seat. Ben does point out that Clancy will be included along with the blast, yet he says that it won't, and a colony of cockroaches pour out of his clothes, forming a makeshift suit around him. Gwen realizes that the cockroaches will be the ones only to survive the blast.
Ben transforms into Heat Blast to stop Clancy, but his cold encounters the same problems his previous forms did. This time, Heat Blast's body shifted from the normal color of red and orange, to a color of red and blue. Gwen points his condition out, but he says that there isn't time and has her head to the reactor. They run, while Heat Blast tries to attack Clancy. The suit of cockroaches augmented his strength, and bats Heat Blast away easily. Clancy then sends wasps to deal with Gwen and Grandpa Max. Heat Blast tries to fry Clancy, but nothing happens and he sneezes. Ben realizes that his flames are frozen, and Clancy attacks him again.
In a hallway, Gwen and Grandpa Max are fleeing from the wasps. The voice announces that a core meltdown will occur in five minutes. They approach the end of the hall, and find a hose. They use it to spray them down. Back at the control room, Heat Blast continues to be beat up by Clancy. He tries to get Clancy to talk, and accidentally triggers his abnormal power to control cold instead of heat. Back at Gwen and Grandpa Max, they make it at the main reactor room, yet to be followed by more insects. At this point, the automated voice announces that they only have one minute to go, intensifying the situation. As Heat Blast continues to fight Clancy, Gwen and Grandpa Max try to shut the reactor down, Heat Blast freezes his arm of cockroaches, yet it grows back and tackles Heat Blast through the window. Heat Blast makes an icicle to slide down to the floor, which surprises Gwen. Grandpa Max warns him this time, giving Heat Blast enough time to make a large ball of cold energy to toss at Clancy, completely freezing him. He then turns to the reactor and freezes it, just in time to bring the temperature down. Gwen and Grandpa Max congratulate him, and Ben suggests that they get some hot chocolate.
In the end, Ben has gotten over his cold. With Clancy defeated, and the nuclear plant neutralized, everything seems to have worked out. Gwen gets some milk when a roach crawls out from under the refrigerator. She prepares to smash it, yet many more insects begin to crawl over every surface of the RV, bringing it to a stop. Clancy is back with his suit of cockroaches, and he lets himself in to get revenge. Grandpa Max tries to attack Clancy, but dodges him and tosses him into the front of the RV. He walks over to deal with Grandpa Max, while his cockroaches deal with Ben and Gwen. Ben tries to activate the Omnitrix, yet it does not work. Gwen tells Ben that she thought he froze him earlier. He points out that Clancy must have thawed out. Gwen tries to spray the bugs away with the fire extinguisher, and Ben asks how they will be able to stop them. Gwen makes a point that there is a way by attracting them with a candy bar, which gives Ben an idea. He retrieves the San Ju Yen Pien he had hidden earlier and opens it. All the bugs, including Clancy's suit, move towards it. Ben tosses the medicine out to get rid of them. Clancy is now without backup, and Grandpa Max easily knocks Clancy out cold. Gwen says she's happy that he's out cold, and he was starting to bug her, and sneezes. Ben is happy about this, and saying that everything really did work out for the best. The episode ends on that note.