Sometimes we reenacted our father's injury by smearing berry juice on Hannah's hand. "It hurts!" she said.

I peered at it worriedly. "I think it's going to leave a scar." Other days, we played the Dead Auntie game. My mother's sister had died when my mother was still a child. When we still lived in Korea, we followed our parents up the mountains to the graves of our ancestors to offer them food and wine on the day of the harvest moon, and I wondered why we left my aunt's burial mound unattended. In front of the other graves we shouted out our names.

"Grandfather, we are here! Haejini and Jeehyuni! We are saying hello!"

We bowed to our grandparents, then to their parents, then to the seven generations of ancestors buried on that mountain.

The path to my aunt's burial mound was overgrown, full of snakes and biting insects. We did not bow in front of her grave, or call out our names. My mother quietly trimmed the grass that grew over the mound with her long curved blade, chanting the Buddha's name.

Once Hannah cried out exuberantly, "Auntie, we've come to visit you!" and my mother knelt and slapped her in the face. After that we were not allowed to visit that grave, but waited for my parents at the edge of the path and played among the trees that shaded the mountain, tapping long sticks on the ground to keep the snakes away. Hannah swore she saw a woman following them once, picking her way through the overgrown path, her long white dress catching on the brush underneath and snagging on the trees around her. Hannah swore she heard her singing as she braided her long black hair.

The adults would never tell us how our auntie had died. But alone, we pretended I was Auntie, and Hannah was our mother. Sometimes we switched roles so I could play the bad guys who killed her, or the doctor who diagnosed her with a fatal disease. We would actually weep as we played this game, imagining my mother's family at the news that our auntie was dead. I always played our auntie brave, never giving up hope to the very last, never betraying national secrets to the North Korean spies, always standing up for what she believed in and protecting those she loved.

The year I became a math major, Hannah and I started growing apart. She never understood my chosen field, and considered it a defection to my father's fortress of reason and logic.

"You can't even divide up a bill," she said. "You're horrible with numbers."

I tried to tell her about complex and imaginary numbers, primes and transcendentals, numbers with families and personalities, but she rolled her eyes.

"I don't know how you can think any of that is important," she said. She was studying to become a biologist, deep in the gunk of life and committed to saving the earth, and could see no beauty in what I did.

But math had come with me from Korea to America, and its familiarity had pulled me through those first bewildering years. I liked its solidity, the possibility of discovering a truth around which no further argument need swirl. And Hannah was right to feel left behind, maybe even betrayed. Because something changed between my father and me when I started talking shop with him. My father had always wanted a son. We women were unreliable creatures, prone to fits of emotion and flights from logic that generally ended with him at the receiving end of a pointed finger. "Yes!" he'd said, when I told him I'd decided to study math. He reached out his hand and said, "Shake!" While he pumped my hand up and down, he said, "Math lasts."

One day in the summer after my sophomore year of college, my father and I tried to construct the seventeen-gon with a straightedge and compass. As we talked, something in him eased up and fell away. He laughed, made jokes about our family in mathematical terminology. When we talked math, the words flowed, pure and easy. Here were rules we could both abide by, here was a language that was eloquent, and spoke to us about the world. Later, we sat in our backyard going over what I thought at the time was a particularly complex proof. My mother's roses were in bloom at the edge of our lawn, and we could smell them faintly, their perfume drifting over on the occasional breeze. A beetle flew onto the picnic table and landed on our paper.

Excerpted from Forgotten Country by Catherine Chung. Copyright © 2012 by Catherine Chung. Excerpted by permission of Riverhead Books. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.