At Pearl Bailey High School, Steve's class is being lectured about Black History Month by a white man. His teacher orders the class to write a paper on a figure in black history.
That night at home, Roger tries to get Steve to play Jenga but he's busy trying to write his report and can't decide on a topic. Francine suggests he do his report on George Washington Carver, the inventor of peanut butter. Steve thinks it's a great idea and goes off to write his paper. Francine is elated that someone took her advice so she gets some celebratory wine and goes to take a bath. Roger tries to get Hayley to play Jenga with him and she decides to up the stakes by introducing gambling into the game.
Steve is writing his paper in his room when Stan comes in and tells him to get to sleep. He also tells him to write his paper on someone more interesting than George Washington Carver. Steve tells him he is too old to be told what to do. Stan, of course, doesn't listen.
Steve is at the grocery store with his friend researching peanut butter for his paper when he spots something on the label of the peanut butter jar. It is a symbol of a peanut inside a triangle and he also finds it on all the other peanut butter labels. He vows to get to the bottom of the mystery.
Steve asks his teacher for more time to research his paper but he won't allow it. Steve decides he is going to find the answer regardless of what his teacher says. After Steve leaves, his teacher makes a phone call to a shadowy group sitting around a triangular table. He says that they have some "chocolate in their peanut butter" and the man answering the phone gets mad and crushes a peanut.
On a rainy night, Steve is at a payphone calling the Smithsonian Peanut Museum for more information on George Washington Carver. The curator on the other end tells him to come to the museum but to be careful because he is being watched. A car almost crashes into him but it's just a drunk driver. When he shows up at the museum, a detective tells him the curator has been killed. They find the curator's body stuck to the roof of the mouth of a huge statue of George Washington Carver. The detective also points out that he has left a message in his own blood on the floor - "In the Elf Condom". Steve tries to figure out what it means. He realizes it is an anagram for "Find the Monocle". In the curator's study, he tries to figure out the mystery but is distracted by the sound of a ticking clock. He sees the pendulum is a monocle with the peanut/triangle symbol on it so he grabs it just before a security guard shows up.
Meanwhile, back at the house, Hayley and Roger are playing Jenga but Roger takes hours to make a move annoying Hayley.
Steve is walking down the street trying to solve the mystery when a man gets out of a black car and tells him to get in because he's won a free air conditioner. He's about to get in when he sees the peanut/triangle tattoo on the man's neck. He is alarmed and the man pulls a gun and tells him to get in the car. At that moment, the drunk driver from earlier crashes into the black car, giving Steve a chance to get away. More armed and dangerous men get out of the black car and chase Steve into an alley. He is cornered when a man rappelles down from the building and rescues him. It happens to be Stan. Stan tells him that he has stumbled upon the biggest conspiracy in history. He tells Steve he's in over his head and that he should do his report on someone else. Steve shows him the monocle so Stan says that this conspiracy is not child's play. Steve objects and tells him that he's not a child. Stan agrees to solve the mystery with him. They go to a safe-deposit box and Stan shows Steve some documents. He shows him a picture of Lincoln and two advisors. Lincoln and his advisors talk about how to get southern white people to accept freed black slaves when one of the advisors eats a cracker with peanut butter. He asks Lincoln what peanut butter is, and Lincoln says it's a strange concoction that his wife created. They all eat the peanut butter and agree that it is delicious. Lincoln comes up with a plan to give peanut butter to the South and say a black man developed it with the logic that if the Southerners liked peanut butter, they would like black people. Unfortunately, John Wilkes Booth got wind of the plan and killed Lincoln before the plan could go into effect. 31 years later, President Grover Cleveland resurrected the plan and gave the recipe for peanut butter to George Washington Carver. Stan says how the nation was healed by the discovery of peanut butter by a black man and that they are the only people outside of the IllumiNUTi who know the real story. He says the IllumiNUTi are a secret society whose mission is to keep the secret hidden and are the people with the peanut/triangle tattoos. Steve wants to blow the lid off the conspiracy and Stan tells him that to do so they must show the "Jar of Proof" showing the physical evidence that Carver didn't invent peanut butter. Steve shows him a map that can only be read by a special ocular device that shows where the "Jar of Proof" is. The monocle is the ocular device that allows them to view the map. At Burger King, they use the monocle to decipher the map. They find the next stop on the trail - an old strip club. As they go there, they are watched by a shadowy figure.
Roger and Hayley still play Jenga. Roger loses on his first move but cheats to get back into the game.
Stan and Steve go to the strip club and find the peanut symbol on the pole. They need to get the pole so Steve tells the strippers there is a toddler locked in a car in the parking lot who has found a stash so all the strippers run out to see if it is their child.
Roger and Hayley playing Jenga but Roger has brought in an engineer to help him cheat.
Stan and Steve attach the monocle to the pole and wait until sunup to for it to show them where to go. They place the map on the ground. When the sun comes through the monocle, it burns the map and Stan gets mad that he destroyed the map. Steve blows away the ashes to reveal the final clue - "Lastly tip your hat in the Garden of Eden". Stan tries to call an airline to get a ticket to the Garden of Eden but Steve finds out that they mean the first National garden. They go there and dig up a peanut tree but don't find anything until they see the bottom of the planter has a clue - a picture of a hat. They realize that it's a reference to Lincoln so they go to the Lincoln Memorial. They put the monocle on Lincoln and the statue moves and let's them enter to find the proof. The same shadowy figure watches them angrily. Stan and Steve make their way down the cave.
Roger and Hayley are still trying to play Jenga when Roger finally makes a move. He then gets mad at Hayley for taking 10 seconds to make a move.
Steve and Stan find the Jar of Proof but as Stan reaches for it, Steve notices the IllumiNUTi tattoo on Stan's back. Steve goes for the Jar of Proof, containing the names Lincoln came up for peanut butter. He switches it with a jar of peanut butter before Stan can take it. Steve confronts Stan and says that he's one of the IllumiNUTi. Stan tells him to give him the jar because the lie was the only thing that kept the nation together. Jimmy Carter shows up and agrees with Stan. Carter takes the jar and jumps into a river of lava to destroy the proof.
Stan and Steve run away. Steve is a little sad because now they can't spread the truth. Stan agrees so they decide to put the answer to the mystery on Wikipedia.