This episode starts out with Dib doing a report on Galileo, saying how nobody believed him, when Ms. Bitters interuppted him and told him that time was up, and asked if anyone had any questions. Zita raised her hand and told him that he was crazy, and Ms. Bitters gave her an A. Melvin came in with telling Ms. Bitters sorry that he's late, his head itches, and started scratching it, spreading lice around. The whole Skool broke out with lice, everyone except for Zim, but he tried his hardest to pretend. Ms. Bitters pressed a red button on her desk, and three people came up out from the floor. A guy used a red scanner thingy and told the head woman, Countess, that it was a level one infestation. She told them that they all have lice, and for their own good, they will be detained there indefinitly. She said let the de-licing begin, and a sheet fell over Skool.
In the auditorium, she told them that they have been seperated by severity, and the worst people were most of Ms. Bitter's class and Gaz. The ones without lice were on the stage, Ms. Bitters and Zim. Zim went to the microphone stand to tell them that he would like to take the oppertunity to tell them that if were a member of an alien race, which he is not, he would like to say, "FILTHY EARTH CREATURES! IT'S CLEAR WHO THE SUPERIOR RACE IS AND-" but got cut off because Dib threw a paper ball at him. One of Countess' men picked Zim up and sat him back down. Countess told them that the two clean ones will be taken to a special area for immunity research, and the rest of them will be taken with her assistants for their assignments.
Dib was parntered up with Melvin, being escorted down the hall, where they peaked into other people being treated. One kid was getting his hair shaved off, Spoo was turned upside down to be dipped into a bucket of anit-lice stuff, and Rob was getting his lice picked out by a monkey. Dib and Melvin were thrown into a room where a bucket full of soap and some other horrible looking machine awaited them. Dib grabbed Melvin and dragged him to the window, where he tried to escape, but Countess was right there. Dib told her that she won't get away with it, and she told him when she's through she'll be looked upon as a hero. She told them to take their seats, and she used some kind of machine to but the soap stuff on Melvin. She was about to move on to Dib, but she was interuppted when one of her assistants told her that she was required in B-Wing. She was about to shut the door, but Dib kicked the tool she was using to keep it from shutting. He told Melvin that it's obvious the de-licer has become mad with power, and Melvin asked if he meant she was crazy. He told him that they've got to tell the world what is going on. He runs down the hall when he sees the Immunity Research room and peaks in. One of the assistants told them that they need a skin sample to see what makes them immune, and Zim told him that he was like all the other humans, loaded with lice, but they were just in his belly. He was about to move to Ms. Bitters, but she told him to take it from him. In another room, Gaz was hooked up to some kind of machine playing her game, when she heard Zim scream, and called him a whiner.
Dib heard Countess talking, and he went outside of the room she was in to listen. One of the assistants told her that fifteen of the test subjects disappeard, and she asked if he meant escaped. He told her that they wouldn't have made it past the mine field, they're just gone, and she told him to got tell security. She started rambling on how she there were research oppertunitys from an infestation that size, but there was something more to the disappearances, and that there probably was proof of a mastermind queen lice, and she will stop it. Dib told Melvin that she's crazier than he thought, and told Melvin to keep quiet, but he screamed about the lice queen. One of her assistants found them asked what they were doing out there, but Dib asked him what he was doing out there. He went crazy, saying that he was using mind tricks, and Dib and Keef ran. The assistant that was doing the immunization research and Countess ran out of there roons. She told the immunization reasearch assistant to continue his studys, and she'll handle it.
Dib and Melvin ran into a room where there were hundreds of machines picking lice out of kids, and a shadow passed the door. Dib said that he lost her, but Countess was already in there. She told them she knew they would be trouble, and pulled out a taser, narrowly missing Dib and Melvin's head. Dib told her that all of this needs to stop, but she told him that he didn't get it. Dib told her that it was just lice, be she told him he couldn't see the full extent of the problem, it was much bigger than he knew. Dib told her that she was insane, and there is no lice queen, but the floor caved in and they all fell through.
They were in what seemed to be a giant tunnel, and Dib saw a giant lice. Countess told him that she found the queen and the nest, and that she was right. The queen lice got off of the nest and tried to attack every one. One of the assistants told Countess that the green child's (Zim's) skin destroys the lice, and threw down a gun and Zim. She put Zim in the gun, and told him to close his eyes, and fired at the queen. She fired at the kids, killing all the lice on them.
When she was done, she got to Dib. He told her that she was right all along, and told her sorry. She told him he should be, and fired at Dib, killing the lice on him. She pulled a half skinless Zim out of the gun, and told them that thanks to the bravery of him, the world would never have to deal with lice again. Zim started screaming about the pain, and Gaz, from somwhere else, screamed whiner. Countess continued on, saying that future generations will sing songs about him and his fight against headlice. Dib grew a little jealous and told her that he was an alien, but she ignored him, saying that her work was done.
Back in the immunity reasearch room, Ms. Bitters sratched her head for a few seconds.