While the boys are waiting for the school bus, Eric Cartman explains the odd nightmare he had the previous night involving alien visitors abducting him and probing him when he went to bed. Cartman's friends, Kyle Broflovski and Stan Marsh try to convince him that the dream was reality. Meanwhile, Ike is abducted.
In beginning of the episode, Cartman details his dream of being abducted by aliens and receiving an anal probe. The others try to convince him it was real, but Cartman assumes they're just trying to scare him. Chef then pulls up and asks the boys if they saw a visitor spaceship, inadvertently confirming the reality behind Cartman's "dream." Chef is also wearing a T-shirt with a picture of an alien "visitor" on the back with the word "Believe", scaring Cartman even more. After Chef leaves, the school bus shows up, introducing Ms. Crabtree, a scary-looking, loudmouthed, middle aged school bus driver who constantly tells the children to "Sit down and shut up!" As the bus is driving away, Kyle looks back and sees his brother Ike, being held by two visitors.
Meanwhile, Officer Barbrady investigates another cow mutilation on Jenkins' farm. Several other visitors try to lure away cows by whistling and offering straw. The cows aren't falling for the trap as several of them have been turned inside out. Barbrady explains that a cow turning inside out is nothing unusual, clearly revealing that he's an incompetent law officer. Also, when helicopters fly by and the farmer asks what they were, Barbrady says they were pigeons.
The boys are now at school. Worried about his brother (and how his parents will react), Kyle asks Mr. Garrison if he can be excused from school to find his brother. Mr. Garrison tells Kyle he has to ask Mr. Garrison's puppet, Mr. Hat. This is when Mr. Garrison and Mr. Hat's shared catchphrase of, "You go to hell! You go to hell and you die!" is introduced. Cartman laughs at Kyle and ends up farting fire (due to the anal probe) at one of the children(whom we later discover is Pip Pirrup, in "Damien").
After being told Kyle's brother was abducted by visitors, Chef freaks out and says, "What the hell do you think you're doing in school eating Salisbury steak? Go find him, dammit!" This is when a cyclops-like robot pops up from behind Cartman and quickly retreats from whence it came. This ends up being the anal probe from Cartman's "dream". To help the children find Kyle's brother, Chef pulls the fire alarm.
When the children get out of school, Cartman still doesn't believe that he has gotten an anal probe from the visitors. While insisting that he is not under mind control, a beam from above hits him out of nowhere as he suddenly sings "I Love to Singa". The children use this as proof that Cartman is being controlled by visitors. Cartman, in all ignorance, still disagrees with their idea.
Just then, a spaceship appears. Kyle demands that they return Ike. In response, the aliens blast Kenny with a star-shaped object. Which causes Kenny to fly into the street, and he appears to be dead. Stan and Kyle respond by saying, "Oh my God! They killed Kenny!" "You bastards!" for the first time. Kenny, however, isn't dead yet. He stands up, only to be trampled by the herd of cattle that ran away from Jenkins' farm. Kenny is still alive after this. He is finally killed when Officer Barbrady, in pursuit of the cattle, runs over him in his police car. Despite this, Cartman still denies that the visitors are real and that Kenny is actually dead. He decides to go home.
Stan and Kyle go to Stark's Pond to meet Wendy, although Kyle wants to keep looking for Ike. Wendy shows up, and Stan vomits when she speaks to him. Kyle tells Wendy what happened to his brother, and she suggests that they use Cartman as bait to draw the aliens back.
To lure the visitors back, Stan, Kyle and Wendy tie Cartman up to a tree. After Cartman farts flames several times, an 80-feet wide satellite dish protrudes from his rectum. After the visitor spaceships show up, Ike is revealed behind a door on a ship. Kyle, in trying to get his brother to jump down, tells him to do his impersonation of David Caruso's career. Before jumping out, the visitors talk to the cows. The visitors tell the cows that they are the most intelligent life form that they found on Planet Earth. The cows want to know why they turned some of their cow friends inside out, the visitors explain that it was "Carl's fault, he's new" and give them a device that makes people sing. Before leaving, the visitors abduct Cartman again.
Meanwhile, Officer Barbrady find the cows, and demands them to come back, but the cows use the device the visitors made on him, and makes him sing I Love To Singa.
The next morning, Cartman falls from the sky and lands at the bus stop. One of his eyes is red. He immediately describes to Stan and Kyle a "dream" he had about getting pinkeye from Scott Baio aboard the alien spacecraft.