Heads up: this time frame puts the events of the novel in chronological order as the characters experience them in their lives. This is not the order we read them in, since the book is a series of flashbacks and flash-forwards – so if you don't want any details spoiled, come back when you finish the book!
Once upon a time, in a town in India called Ayemenem, there was an Imperial Entomologist (someone who studies bugs) named Shri Benaan John Ipe, who we will refer to henceforth as Pappachi (grandfather). One day Pappachi discovers what he thinks is a new breed of moth. It's the biggest thing that has happened to him. He's devastated to be told that all he found was an abnormal breed of an already-existing species. Later on, the powers that be decide they were wrong, but the new moth is named after a different scientist. Pappachi will resent this for the rest of his life.
Pappachi is married to Mammachi, an accomplished violinist, whom he beats. Pappachi and Mammachi have two children: a daughter named Ammu and a son named Chacko. Chacko goes on to study as a Rhodes Scholar at Oxford, where he marries a white woman named Margaret. They have a daughter named Sophie. While she's pregnant, Margaret falls for a guy named Joe, whom she marries after divorcing Chacko. Chacko is heartbroken and moves back to Ayemenem.
Meanwhile, Ammu, seeking a little excitement in her life, moves out of her parents' house to live with an out-of-town relative. She meets Baba and marries him. In 1962, they have twins: a boy named Esthappen Yako (Estha) and a girl named Rahel. It turns out Baba is not only an alcoholic, he also tells lots of lies, big and small, for no apparent reason. One day Baba loses his job, but his English boss says he will work something out for him if Baba will let him sleep with Ammu. Baba runs this indecent proposal by Ammu (like that's going to go well for him...) and beats her when she refuses. Ammu takes the kids and moves back to Ayemenem. So that's it for our back-story.
A major chunk of the novel takes place in 1969, when the twins are 7 years old. Joe is killed in a car accident, and Chacko invites the grieving Margaret Kochamma and Sophie Mol to come to Ayemenem for the holidays. Chacko, Ammu, Baby Kochamma, Estha, and Rahel drive to Cochin to get them at the airport. On the way, two big things happen. First, traffic stops almost entirely when a huge march of communists floods the streets. Rahel is really excited to see Velutha, who does the maintenance work at Paradise Pickles and Preserves, Mammachi's factory. He's waving a red flag. When she calls his name, he disappears into the crowd and things get tense in the car.
The second big event on the way to Cochin is that the family goes to see The Sound of Music, which is the twins' favorite movie. Estha has to go stand in the lobby because he can't stop singing along. While he's alone in the lobby, he is molested by the Orangedrink Lemondrink Man. This experience fills Estha with unending fear.
The family stays overnight at a hotel, and the next day they meet Sophie Mol and Margaret Kochamma at the airport. Rahel worries that Ammu will love Sophie Mol more than she loves her. When they get back to Ayemenem, everyone makes a fuss over Sophie Mol. Rahel feels like she's playing a supporting role in a play in which Sophie Mol is the star. She runs off to talk to Velutha, telling him she saw him in the march. Velutha tells her a fib, saying the person she saw was his long-lost twin. Ammu sees them together and we start to realize that Ammu and Velutha dig each other in a major way.
Meanwhile, Estha is completely terrified because the Orangedrink Lemondrink Man knows where he lives and can come for him any day. He runs into the factory and thinks Two Thoughts while he stirs a pot of banana jam. These thoughts are: Anything can happen to Anyone, and It's best to be prepared. Estha thinks about getting a boat and rowing over to the History House, a deserted home that once belonged to an Englishman who "went native." He figures the Orangedrink Lemondrink Man won't be able to find him there. When Rahel finds him rowing the jam like a boat, Estha tells her about his plan. They end up finding a small rowboat and get Velutha to fix it up for them.
Not too long after this episode, Vellya Paapen, Velutha's dad, comes to the door crying. He tells Mammachi and Baby Kochamma that Ammu and Velutha are lovers. This is a big no-no, since their society is driven by class rules, and Ammu is much higher up. Velutha is what is known as an Untouchable, basically meaning that he's the lowest of the low in Indian society. In their world, an affair like this is totally unheard of.
Baby Kochamma and Mammachi trick Ammu into going into her room and they lock her in. When Estha and Rahel come to the door and ask Ammu why she's locked in her room, she screams that it's their fault. Estha and Rahel decide it's time to hightail it out of there. Sophie Mol convinces them that she should go, too, so that the grownups will be really sorry (famous last words, Sophie...). That night they get in the boat and start rowing across the river. They're almost all the way across when a log collides with the boat and topples it over. Rahel and Estha swim to the other side, but when they call for Sophie Mol, she doesn't respond. They realize that she's drowned. They end up falling asleep in the History House, not realizing that Velutha is asleep in the corner waiting for Ammu to meet him for their nightly rendezvous.
In the meantime, Baby Kochamma and Mammachi have decided to try to get Velutha to skip town so the whole family can avoid the shame of being associated with him. The problem is, before they can put their plan into action, Sophie Mol's body is found. Time for Plan B. Baby Kochamma goes to the police, making up a bogus story about how Velutha tried to rape Ammu and kidnapped the kids. In the meantime, the police come to the History House and savagely beat the living daylights out of Velutha. He survives the beating for the time being, and the police drag him away. Rahel and Estha see the entire incident.
Later on, Inspector Thomas Mathew tells Baby Kochamma that she has no case – Rahel and Estha don't seem to have been abducted, and it's pretty clear that Baby Kochamma made everything up. Since her butt is on the line, Baby Kochamma freaks out and asks to be alone with the kids. She blames Rahel and Estha for Sophie Mol's death and tells them that because of what they did, Ammu will be jailed and will most likely die – unless they rat out Velutha. She tells Estha that the inspector will ask him one question and that his response to it should be "yes."
At Sophie Mol's funeral, everyone ignores Rahel, Estha, and Ammu, who stand apart from the rest of the family. After the funeral, Ammu goes to the police station to clear Velutha's name. Inspector Thomas Mathew tells her it's too late – Velutha is dead. Baby Kochamma freaks out when she finds out that her story has been pulled apart yet again. She decides to get Ammu out of Ayemenem. She finds that it's not hard to exploit Chacko's grief to set him against Ammu. Ammu has to go out on her own and fend for herself. Estha is returned to his father, Baba. Rahel stays with Mammachi and Baby Kochamma, who eventually send her off to school.
Rahel is kicked out of school a few times for misbehavior. The last time she sees Ammu is when she's 11 and Ammu is 31. Ammu looks awful and is suffering from a lung disorder, most likely tuberculosis. When Ammu dies, Rahel and Chacko go together to have her body incinerated.
Rahel goes on to study architecture in Delhi and eventually moves to the United States. She marries a man named Larry McCaslin. He loves her but is troubled by how distant she seems when they make love. They eventually get divorced. Rahel works random jobs in New York and Washington. When she is 31, she finds out that Estha has been "re-Returned" and goes back to Ayemenem.
The Ayemenem House in 1993 is totally different than it was in 1969. Baby Kochamma has discovered satellite TV, and all she and Kochu Maria (the housekeeper) do is watch television while the rest of the house lies in a shambles. Baby Kochamma tells Rahel that she doesn't know what to do with Estha. Since the day he was Returned to Baba, Estha has given up speaking entirely. He goes on long walks around Ayemenem without telling anyone where he's going.
Being back in Ayemenem brings back a flood of memories for Rahel. The twins go through old items like their Wisdom Exercise Notebooks and look at little trinkets that they collected as kids. Rahel and Estha spend a lot of time together. They end up having sex and holding each other for a long time afterward. The narrator acknowledges that, like Ammu and Velutha, Rahel and Estha have violated the Love Laws that "lay down who should be loved. And how. And how much" (20.78).