Lincoln is explaining to the viewers that tomorrow is April 1st, which is April Fools' Day. Luan becomes a sadistic pranking monster on this day every year, so Lincoln, the rest of his sisters and their parents are all scared of this day. He shows some footage of the past April Fools Days, showing that Luan is unstoppable (like nailing the living room furniture upside down, placing chickens in the living room, covering the entire house with present wrapping paper, trapping all of her siblings in a giant block of gelatin, and shaving all of the Loud pets' fur and feathers off). Lincoln plans to stay in his room for the entire day, while his sisters are preparing to defend themselves. Lisa builds a bomb shelter to take cover in and the others add body protection, mostly consisting of plastic bubble wrap.
After boarding up his entire door, Lincoln calls up Clyde if he wants to come over. However, Clyde refuses to come over, knowing about Luan's pranking spree. Just then, Lincoln gets a text from Ronnie Anne telling him that she's coming over to give him a present. Lincoln is scared because he'll have to exit the confines of his room and if Ronnie Anne gets pranked, she'll severely hurt him. Clyde suggests to Lincoln that he go face-to-face with Luan and call off April Fools. He does so, but Luan refuses to back down, stating that anyone who falls victims to her pranks is fair game. When Lincoln heads back to his room, he comes up with a plan to prevent Luan from pranking all of them. He tells his sisters that if they work together, they can take Luan down. That night, in Luna and Luan's room, Luna gives a bird-like call signal to her siblings. Everybody then enters the room and tie down Luan, trapping her in a cage and keeping her fingers together with Chinese finger traps. The siblings mock Luan's situation while she looks on in anger.
The next day, however, the siblings are shocked that Luan broke out of her cage and that she could be anywhere in the house. Almost immediately, the pranks are being set off so they all take cover. As all the siblings take shelter in Lincoln's room (with the exception of Lisa, who takes cover in her bomb shelter), Lincoln remembers that Ronnie Anne is coming by later. Not wanting her to get pranked, Lincoln decides that the best thing to do is to set off the pranks in the house to save Ronnie Annie from them. The sisters wish Lincoln good luck, with Lucy saying she will prepare for his impending funeral.
Lincoln runs downstairs and heads to the kitchen where the entire floor is covered in grease. After taking one step, he loses his footing, gets socked in the face by a boxing glove on a spring and gets attacked by vicious raccoons, all while Luan looks on with pride. Mr. and Mrs. Loud, who are also terrified by Luan's pranking spree, beg for Lisa to let them into her bomb shelter, which she does. As the sisters hide in Lincoln's room, Lori suggests that they ration the food supply, but Lana has eaten it all, much to everyone else's exasperation. Leni nominates herself to get more food from the kitchen, but thanks to a bunch of misleading signs placed by Luan she wanders out of the house and into who-knows-where in the city.
Lincoln then takes on the bathroom where he is covered in flour, sprayed by the sink and attacked by another vicious raccoon. Next, he tackles the living room which results in him getting flung into the ceiling and getting stuck in flypaper. The last thing Lincoln has to do is set off all the pranks in the bedrooms (with Clyde taking on Lori and Leni's room). When Clyde collapses on the sidewalk, Ronnie Anne arrives and is shocked to see Lincoln in critical condition. Luan declares victory, but Lincoln claims that he did it to save Ronnie Anne from humiliation. Luan then reveals that she called Ronnie Anne to come over, thus giving a reason why Lincoln had to leave his room, and that she is the final part of her plan. As Ronnie Anne pulls out a pie, Lincoln embraces for impact, but she instead pelts Luan with the pie. It turns out that Ronnie Anne appreciates Lincoln sacrificing himself to Luan's pranks for her and pelted Luan instead of him as a sign of gratitude. The two then depart so Ronnie Anne could put Lincoln's eyebrows back on while Luan looks on with pride, saying that Ronnie Anne is a keeper.
As Lisa, the parents, and the remaining sisters exit their shelters, they are relieved that they didn't get pranked. However, they realize that Leni's missing and Lisa deduces that the signs that mislead Leni earlier are the cause of this. Mr. Loud prompts everybody to get in the car, but when they start it the airbag explodes, splattering blue paint all over the interior of the car. As the family yells out Luan's name in fury, the latter is depressed that April Fools is over and that she's feeling blue now (alluding to the blue paint joke she just pulled off).
Lily has no lines in this episode.