The story of the upside-down house comes to represent the polarizing power of borders and the stories people tell about them. After Tha'mma's father and Jethamoshai divide their house in half with a wall, Tha'mma tells Mayadebi, who was too young to remember when the house wasn't divided, that their aunt, uncle, and cousins do everything backwards. She insists they drink tea out of buckets, and eat dinner at breakfast time. Over time, Tha'mma almost comes to believe this fantastical story she tells, if only because she never goes to the other side after the division. Tha'mma crafts the story that the people on the other side are very different from her, when in reality, they're no different—and in fact, are family.
The The Shadow Lines quotes below all refer to the symbol of The Upside-Down House. For each quote, you can also see the other characters and themes related to it (each theme is indicated by its own dot and icon, like this one: Note: all page numbers and citation info for the quotes below refer to the Houghton Mifflin edition of The Shadow Lines published in 2007.).
The timeline below shows where the symbol The Upside-Down House appears in The Shadow Lines. The colored dots and icons indicate which themes are associated with that appearance.
2. Coming Home
...admits that there's one regret she has about Dhaka: she never got to see the upside-down house. She explains that she told Mayadebi that on Jethamoshai's side of the house, everything... (full context)
...courtyard and into a grimy room in the house. Mayadebi and Tha'mma laugh: nothing is upside-down. Khalil sends his wife to make tea, and the guests finally notice Jethamoshai on a... (full context)