The following version of this book was used to create the guide: Rooney, Sally. Intermezzo. Farrar, Straus, and Giroux, 2024.

Sally Rooney's novel Intermezzo is set in present-day Ireland and written from the third person point of view. The narrative employs both the past and present tenses and toys with conventional notions of linearity. The following summary relies upon the present tense and employs a streamlined mode of explanation.

Peter Koubek and Ivan Koubek's father dies. After the funeral, 32-year-old Peter tells his college girlfriend Naomi about how strange his younger brother Ivan is and how odd his behavior was at the funeral. Throughout the weeks following, Peter tries to hide from his sorrow by getting drunk with Naomi and visiting his close friend and ex-girlfriend Sylvia Larkin. He and Sylvia broke up years prior after Sylvia suffered a life-altering accident. They still love each other but Sylvia is afraid of ruining Peter's life. Peter continues spending time with her although he's falling in love with Naomi. He self-medicates almost every night so he does not have to think about these issues.

Meanwhile, 22-year-old Ivan is heartbroken and frustrated after the funeral. He tries to distract himself by doing freelance work and participating in chess competitions. One weekend, he travels from Dublin to Leitrim for another event. While here, he meets the town hall arts director, 36-year-old Margaret Kearns. They feel an instant connection with one another. After the competition, Margaret drives Ivan to his rental, where they kiss and have sex. Over the course of the following weeks, Ivan starts to visit Margaret in Leitrim every weekend and they fall in love. Despite their intense feelings for each other, Margaret worries that their relationship is unsustainable because of their age gap. Ivan insists otherwise.

One evening, Peter and Ivan go out for dinner. Ivan feels annoyed by Peter at first, but then realizes that Peter is trying to open up to him about his life. When he confesses that he is still in love with Sylvia, Ivan tells him about Margaret, alluding to her age and the fact that she is still married to her ex. Peter reacts strongly, insisting that the relationship is a bad idea and that something must be wrong with Margaret. Ivan loses his temper, tells Peter he hates him, storms out, and blocks Peter's number.

Peter's mental health suffers over the course of the following weeks. One night, he tries to reignite his relationship with Sylvia. After Sylvia gives him a handjob and lets Peter touch her, Peter thinks everything is returning to normal. That night, he returns home and tells Naomi the truth about Sylvia and ends their relationship. He says she can go and stay in his father's empty house in Kildare until she finds a new place to live.

One weekend, Ivan goes to Kildare with his dog Alexei. He is shocked to run into Naomi when he arrives. They spend some time talking before getting into an argument. Then Naomi goes out with friends. Meanwhile, Peter goes to Sylvia's house and tells her that he broke up with Naomi. Sylvia is furious, insisting that Peter is causing everyone more pain and that they cannot be together. Peter slams a candlestick off the mantel in anger and Sylvia makes him leave. Afterwards, Peter gets drunk and takes the train to Kildare, hoping Naomi will take him back. He is shocked to find Ivan there when he arrives. The brothers quickly get into an argument which ends in a physical altercation. Peter storms out and heads to his mom Christine's house. Meanwhile, Ivan sits alone reflecting on everything that has happened and realizing that he has not been as sensitive to Peter as he could have been.

In the following days, Naomi and Sylvia confront Peter about his behavior and failure to care for himself. They also agree to a new relational dynamic that includes the three of them. Meanwhile, Margaret dispels her worries about being with Ivan and travels to Dublin to see him compete in a chess event. At the Clancy's Hotel, she runs into Peter. They chat until the game ends. Afterwards, Ivan and Peter take a walk, make amends, and agree to spend Christmas together.