Mrs. Garrison announces that there might be lice problem coming to the school and everyone at school is going to be examined. Cartman is convinced that only poor people can get lice, so Kenny is the only one who will be infected. On Clyde's head, Travis, his wife Kelly, their baby and the other lice are getting on with their lives. The kids' line up for their examination, when Clyde is examined his lice are discovered. On Clyde's head, when he sees the examiner Travis realizes that something is going to be changing in their environment soon, because he believes it is going to react to their presence. Travis has a hard time convincing the President and especially the Vice President of the upcoming threat. At the doctor's office, Clyde finds it easier to admit that he has AIDS, rather than admitting to his lice problem. Travis wants to name their baby Hope as in a "hope for chance at tomorrow." Tomorrow may not come, because Clyde has begun taking a shower and begins using the shampoo that will take care of his lice problem. Travis takes Kelly and Hope on the run, they climb up one of Clyde's hair follicles and convince some others to do the same, but down below there is carnage everywhere. When Clyde begins to blow dry his hair, Travis loses his grip on Kelly, but he still has Hope.
Mrs. Garrison tells the students that someone in their school had a lice problem, but Cartman and the students want to know who was infected so that they can execute their rights as children to make fun of that person. On Clyde's head, Travis, Hope and a few others, including the Vice President, have survived the carnage. Travis tries to rally the survivors and the Vice President wants to know who put him in charge. Travis cites God, when he killed his wife. Outside the school Cartman demands that the "lice head" reveal himself. Kyle suspects Cartman, and he suspects Kyle, then Stan, then Kenny. Cartman plans to get to the bottom of it. Travis tries to motivate the others into following him into the forbidden zone. He has one taker plus the Vice President, who has plans of his own. Cartman conducts a test that Kyle recognizes from John Carpenter's 1982 version of The Thing and the test reveals that Kenny had the lice. Kyle knows the test isn't going to show anything, but believing that he's been found out, Kenny runs from the room.
Travis and company reach the forbidden zone. His female companion expresses her feelings for him, but the Vice President shoots her and then trains his gun on Travis. Cartman and the other boys stop at Clyde's house to get him to join them at the park, where they plan to take care of Kenny with bars of soap and socks. Clyde calls Mrs. Garrison, to get him to come to the park and save one of his students. The Vice President shoots Travis in the knees and reveals his plans to go back, repopulate their community and become President. After making his plans known to Travis and telling him that he knows that their world has no conscience, he puts several bullets in the ground. Clyde, feeling the slight discomfort reaches in and plucks the vice president from his scalp and discards him onto the snowy pavement below. At the park, Cartman reads out the charge against Kenny and the boys get ready to take the soap and socks to him. Kyle stops the carnage by admitting he had the head lice, and then Stan admits that he really had the lice, only to be followed by Cartman, who does admit to having concocted the elaborate scheme to frame Kenny. Mrs. Garrison arrives on the scene to tell them that everyone in their class, boys and girls had head lice. As he believes he is about to die, Travis makes a final call out to his wife. He is picked up by a fly that takes him to a new well-established home, in Angelina Jolie's minge, where the lice haven't been bothered in generations.