Greg's parents reveal that they are going away for the weekend and taking Manny with them. Rodrick takes advantage of this and informs Greg that they are throwing a party together, reminding him of The Heffley Brothers. Rodrick sends the "party text" on his phone and tells Greg to bring his "friends" over. Greg invites Rowley over to help, but they both end up doing all the work while Rodrick sits and directs. He locks them in the basement after tells them to get an extra table. Greg loosens the doorknob and takes photos of the party as "blackmail". In the morning, they are let out and Rowley runs home while Greg confronts Rodrick over what happened. They suddenly get a call from their mother Susan, who informs them that Manny got sick, and they are coming home right away. Rodrick tells Greg to clean up, but Greg refuses. Rodrick finally gets Greg to change his mind and quickly clean up the house. As they think they are done, the bathroom door slides, revealing 'Rodrick Rules' on the bathroom door just as Susan, Frank, and Manny arrive. The brothers quickly remove the bathroom door to Rodrick's room, and switch Rodrick's door with the replacement to the bathroom door after panicking.

Following the incident, Frank makes the two boys rake the leaves. Greg demands Rodrick give him advice in return for helping clean up the party. Rodrick gives in and tells him about his 'Rodrick Rules' which deal with getting things done without making an effort. Greg corrects that 'Rodrick Rules' should be 'Rodrick's Rules', but Rodrick's first rule was "no apostrophes". After raking leaves, Greg quickly becomes impatient but is calmed down when Rodrick teaches him how to play the drums. Greg meets his fellow bandmates of Löded Diper, one of whom is actually a 30-something year old man, Bill, who are going to enter a talent show. Greg is also in it, but is assisting Rowley with his magic act, something which he does not think will be a hit. Frank suspects that the boys are hiding something, but Susan is happy to see them getting along. When Frank asks about Rodrick's "bathroom door" not being locked, Greg covers and claims that he accidentally slammed it too hard, explaining why it does not lock properly. Frank and Susan are going away for the weekend again, but this time, they will leave the boys with Grandpa at the nursing home, which Rodrick seems overly eager about.

At the nursing home, Rodrick reveals that the board games contain plenty of Mom Bucks they can use back at home. He gives some to Greg, but his pants get wet during a game, and he is forced to change in the lobby bathroom. Greg accidentally ends up in the women's room where he gets accused of being a peeping tom. A chase through the old folks home ensues, but he manages to get back to the room. Later, Grandpa tells Greg that he knows that he and Rodrick did not want to come, but he admires that they hang out, something that Frank fails to do with his siblings. The next school day, Rowley reminds Greg that he needed to do his life science project and he rushes to Rodrick for help. He gives him his old life science project on the condition that he hand over some Mom Bucks. Greg does so, but upon arriving at school realizes that it is a failed project about plants sneezing.

Greg angrily reveals his blackmail to Rodrick and demands he pay up in Mom Bucks. Rodrick gives $200 but, he accidentally bumps into Susan, who sees the photos, and she and Frank punish both the boys. One of Rodrick's punishments in particular is that he is not allowed to perform in the talent show, though Greg is still forced to perform with Rowley. When Greg tells Rodrick he didn't expect this, Rodrick angrily tells that never would have happened if he hadn't "snitched". As payback, Rodrick reveals that he took photos of the pictures in Greg's diary about the restroom incident and threatens to send them to his friends who will send them to their siblings. They get the phone away from Rodrick, but Rowley accidentally sends the photos. To Greg's surprise, the story at school got twisted to being about Greg winning the top prize at a bingo competition and making a big getaway, making him popular. Greg is still annoyed however as he has to do the talent show with Rowley, but just before entering, Löded Diper approaches Greg about being their new drummer, as their replacement drummer Larry loves magic and would not mind switching places with him.

Greg starts to question whether he should drum or not, but after Rodrick makes a scathing remark to him, he agrees. Upon seeing Rodrick leaving the show upset, Greg goes out to talk to him and explains that he simply wanted him to be proud of him and was worried they will grow apart. Rodrick tells Greg that he does care about him and that they will continue to hang out together. Greg gives Rodrick his position as drummer back, despite his parents' wishes and returns to Löded Diper. Frank and Susan extend Greg's punishment, but Greg says it's worth it and Grandpa then commends Frank for raising two good brothers while Susan excitedly dances to the band's song. Rowley's magic show ends up winning the competition while Löded Diper gains a wider audience thanks to Susan. Despite their differences, Greg and Rodrick's relationship improves.

At the start of the book, Greg Heffley explains how bad his summer vacation was in which after being signed up with the swim team without his consent, he had to deal with practicing at 7:00 AM, being the worst swimmer on the team, being forced to wear his brother Rodrick’s skimpy hand-me-down racing speedo to save money while everyone else wears baggy swim trunks and his older brother Rodrick annoying him about a secret that Greg is trying to keep. After Rodrick puts him in the back of his van and finds every speed bump in town because their mother Susan wants Rodrick to pick him up after swim practice and school, he drops Greg off at school but Greg finds out he still has the Cheese Touch from last year. Luckily for him, he gets away with passing it on to a new student named Jeremy Pindle who doesn’t even know about the Cheese Touch.

Because Rodrick and Greg constantly complain to Susan about having no money, she starts a "Mom Bucks" program to get Greg and Rodrick to get along with each other. Rodrick immediately spends all of his money on some heavy metal magazines, while Greg carefully and sensibly manages his cash. Rodrick has an upcoming science project that he would prefer to do on 'Gravity', but he clearly shows no effort or interest, and asks his family members to do it for him. One time when Rodrick is ill, the parents leave Greg and Rodrick in charge of the house, thinking that Rodrick will not throw a party in his ill state. However, Rodrick jumps off the couch, calls every friend of his, and throws a party, locking Greg in the basement for the whole night. After the party ends the next day, Rodrick forces Greg into helping him clean up by threatening to reveal his secret. When Greg goes to the bathroom to take a shower, he realizes that someone wrote on the back of the door with a permanent marker. They swap the door in the bathroom with a closet door just as their parents come home. Their father Frank discovers that the new door doesn't lock, but to Greg and Rodrick's relief, he does not realize that it has been replaced.

A month later, while Greg was at Rowley's house playing board games, Greg notices Rowley has play money identical to that of "Mom Bucks" in one of the board games and takes it home to put under his mattress. When Greg fails to do his history homework, he decides to borrow an old assignment from Rodrick and pay him $20,000 in Mom Bucks ($200 in real money). Unfortunately, Greg realizes on the bus that the assignment is very badly written, realizing that Frank started doing Rodrick's homework for him once he started high school and is unable to turn in anything for his History class. On top of that, after Greg returns from school, Susan quickly uncovers the scheme when Rodrick tries to cash in every single Mom Buck Greg gave him as a down payment on a motorcycle, and as a result confiscates all of Greg's Mom Bucks, even his real ones. As a punishment, she makes him clean the entire garage, but Greg enlists Rowley to help him do that very quickly.

After Thanksgiving, Susan sends Frank out to the mail to get photos from Thanksgiving, and Rodrick's party is uncovered by a photo that Rodrick’s friend Bill accidentally took using Susan’s camera (in which Rodrick is visible), for which he is grounded for a month despite his denial that he had it. Greg is accused of being an accomplice to Rodrick and is banned from playing video games for two weeks (since he didn't say anything about the party), even though he had nothing to do with the party.

Rodrick starts preparing for the Crossland Elementary, Middle, and High School talent show with his band, despite being grounded. Eventually, Frank ends Rodrick's punishment two weeks early due to his heavy metal band, Löded Diper, driving him insane every single day. Rodrick goes to Bill’s house to practice. With Rodrick gone, Greg invites Rowley over for a sleepover. After Greg unintentionally injures Rowley's toe by putting a dumbbell in a pillow that Rowley kept kicking as a joke, Susan forces him to perform in the talent show with a first-grader named Scotty Douglas, whom Rowley was partners with, in Rowley's absence. They don't qualify during the auditions, but Rodrick's band, Löded Diper, does. Rodrick is so eager to perform at the talent show that he hands in his Gravity science project early but is forced to start over on account of the topic, experiment, failure to meet school requirements, and lack of sense.

Frank tries to persuade Rodrick to give up the show, but Rodrick insists on doing it so that he can send the tape of his performance to record label companies and drop out of school. During the talent show, Rodrick has his band's performance taped so he can send it to record companies to fulfill his wishes, but the video is rendered useless after it is found that Susan (who was taping the video) had talked the whole time and everything she said was heard on the tape, infuriating Rodrick. When his band comes over to watch the talent show on TV for fragments of their performance, they can't see anything as Susan dances on the stage, making the camera shake terribly. The school's judges who were filming Rodrick's band notice Susan and zoom the camera in on her, which means Rodrick doesn't have anything to send to record companies.

Rodrick first accuses Susan of messing things up, with her replying that if he doesn't allow people to dance, he shouldn't play music. He then accuses Greg of the incident for refusing to record the performance for him and they both get into a fight until their parents send them both to their rooms. Later, Rodrick reveals what happened to Greg over the summer to his friends, with Greg leading to tell the audience his side of the story: One summer, Greg and Rodrick had to stay at Leisure Towers, the retirement home where their grandfather lives, but Greg was bored and took out his journal to write in. However, Rodrick stole Greg's diary and ran, but tripped on a board game that was left on the floor. Greg grabbed his diary, ran to the restrooms, and attempted to destroy it, but then realized he was in the ladies bathroom. He was unable find a way to leave without being seen, and so stayed in the stall until he was eventually reported to the front desk as a suspected “Peeping Tom” and removed by security, which Rodrick saw on Grandpa's TV (which is always tuned to the security camera).

Nevertheless, Rodrick tells his friends, who tell their younger siblings, who then tell their friends, which twists the story from going to the women's bathroom in the retirement home to invading the girls' locker room at Crossland High School, thus earning Greg popularity from the boys, the nickname "Stealthinator", and disdain from the girls. The book ends with Greg helping Rodrick with his science project for school called "Do Plants Sneeze?", due to him feeling sorry for the video of Löded Diper's performance at the talent show, which has become a worldwide internet sensation due to Susan dancing in it.

Live-action film

Brad Simpson stated he anticipated a sequel movie if the first film was a success. "Our writing staff are writing a sequel right now, "Rodrick Rules," which would be based on the second book" ... "And, you know, we hope that the people to see a second movie, so that we are in position of going again right away and making another film. I certainly know that the fans would like to see all the books made into movies."[9]

Fox 2000 greenlit the sequel and Zachary Gordon returned as Greg Heffley.[10] Steve Zahn (Frank Heffley), Devon Bostick (Rodrick Heffley) and Rachael Harris (Susan Heffley) also returned. The film was directed by David Bowers and the screenplay was written by Gabe Sachs and Jeff Judah. Principal photography began in Vancouver in August 2010.^{[citation needed]} A few new characters appeared in the film, including Peyton List as Holly Hills. The film was released on March 25, 2011.[11]

Animated film

On December 3, 2021, an animated film based on the first book was released on Disney+.[12][13] On Disney+ Day 2021, Kinney revealed that the first sequel, based on Rodrick Rules, was released on December 2, 2022.[14]