By Booth Tarkington
Penrod who is a boy of 7 is sitting on a fence thinking about how unfair life is. He suddenly has a brilliant idea of what to do with his free time. Duke, the boy's dog, follows his master into a small shed where a large empty box can be found. Inside this box Penrod stores all of his treasures like a lamp, some cigars, a few matches, a pen, and a notebook.
The young boy made an elevator for his dog using string and a basket. When Penrod has nothing to do, he pretends that his dog is someone going up and down the elevator.
His mother and his sister make him a costume for a party, in which the poor boy would have to pretend to be the child Sir Lancelot. When Penrod looks at himself in the mirror, to his horror, he sees that he is dressed in his sister's trousers and other clothes made for girls. When he arrives at the party, he covers his clothes with a cloak that he had found. Penrod is asked what he is wearing, and he says “Nothing.” This inclines the child who asked him this question to think Penrod is naked under the cloak, so he starts shouting that Penrod is naked!
After the play, Penrod heads back home, but on the way he buys himself some candy and a ticket to a small movie. When he arrives at the movie, it starts. Sadly, this entertainment that the not so wise Penrod had chosen was about a drunk man who was beating his family. When he arrives home, Penrod sees that his aunt and cousin had come from the countryside so that they can escape from an outbreak of measles. The boy has the nerve to ask his sister if his cousin and aunt were running away from the girl's father because he was drunk, but luckily this was not the case.
Penrod is in school and he is very bored. In front of him, a girl is sitting with some of her hair resting on his table. He takes the poor girl's hair, dips it into a bottle of ink, then puts the inky strands onto the girl's back. Another boy notices what Penrod had done and draws the word: “rats,” onto the shirt of the person in front of him. After this act, Penrod starts daydreaming about how he can fly and how he is the best person in the world. His teacher suddenly wakes him up from his daze, Penrod insults her.
The teacher forces Penrod to stay for detention. When Penrod goes to her office, she asks him why he spoke such harsh words to her. The imaginative child inspired by a movie he watched lied, saying that his uncle had beaten his aunt and cousin and that he had to stay up all night and soothe them. The teacher forgives Penrod and lets him go home.
When Penrod is at his dancing class, his teacher announces that a ball will take place and that each boy must find a partner. When Penrod arrives at his partner's house, she had given up on him and had chosen to dance with his enemy: Maurice Levi.
The day before the ball, Penrod concocts a poisonous potion which he feeds to Maurice Levi with the intent of making him sick. But Penrod does not succeed, so he jumps off the roof of his barn so that he does not have to go to the ball.
On the way home from school, Penrod is singing as loud as he can when he notices that a young man is trying to impress his sister. When the mischievous boy arrives at the house, he starts annoying the young man. The poor chap gives Pernod one dollar so that he can leave him alone.
When Penrod is in possession of this money, he goes to a second hand shop and buys an accordion for 20 cents, then spends the rest of it on sweets. When he arrives home, Penrod is sick and almost dies from the sweets, but he survives.
One day when Penrod is sitting in his yard he sees a new neighbor who had just moved in, his name was Rupe Collins. When he asks Rupe where he was from, the boy grabbed him and forced him to lick dirt, then to kill some rats. After this encounter, Penrod thinks Rupe is cool, and starts to act like him. When he meets his sister, he fakes a punch and then laughs at her. Even his friends are beginning to get annoyed by his irritating behavior. One day, Rupe Collins arrives in Penrod's yard and starts calling one of Penrod's friends bad names, so Herman and Verman (Penrod's friends) run the bully over with a lawn mower and hit him with a rake, thus sending him to the hospital. This part of the story shows how easily Penrod can be inspired to do bad things and be a bully.
When Pernod's hair is being cut, he is talking to the barber. The boy tells him that if anyone would call him “Little Gentleman,” that person would die at his hands. They get into a heated argument about what Penrod would do to a girl if she said that, then he goes home. Eventually, one of Penrod's enemies hears this and starts calling Pernod “Little Gentleman.” When the irritable boy hears this, he tosses hot tar in the air towards the girl that was bugging him, nobody got hurt, but Penrod gets beaten half to death with a stick by Marjorie Jones.
Penrod and three other boys are in a heated argument about who is fit to be a preacher. So they each start shouting: “Going to heaven, going to hell,” at the top of their lungs, thus getting the most peaceful of them, Georgie Bassit, grounded because of his screams.
On Penrod's 12th birthday, he and his mother go to visit the boy's aunt. When they arrive at the old lady's house, she gives the boy a pocket knife and hot cookies. On the way home, Penrod's mother stops at a friend's house where Penrod would meet a girl named Fanchon with which he was supposed to dance. At the party, Penrod's ex friend Marjorie Jones is annoyed because he will not dance with her, so she pulls him away from the party by his ear. This causes a massive uproar that ends the party.