In May this year, a North Korean defector in her 40s took a call from an unknown number at her office in the South Korean capital Seoul.
It was from her brother, who she had not seen for more than a decade, calling illegally from North Korea after tracking her down.
He was speaking from a remote mountainside near the border with China, and was in dire need of money to help treat another sister's late stage cancer, she said.
Accompanied by a Chinese broker, the brother had spent five hours climbing up the mountain, avoiding North Korean security and desperately searching for a signal on a Chinese mobile telephone. Contact with anyone in the South is punishable by death in North Korea, one of the world's most isolated states.
The broker was part of a growing group of people, mostly Chinese of Korean descent, who use ties on both sides of the border to funnel money to the North, an illegal and highly dangerous operation.
At first, the defector in the South suspected a trick and demanded the caller answer a question that only her brother could know the answer to.
"I asked him to tell me the name of the train station where we were separated. I am now 40 and we were separated when I was 26," she said, requesting anonymity for fear of reprisals against her family. "Then he said he needed money."
Next morning, she wired 15,000 yuan ($2,400) to the broker's account at a bank in China, near the border. His wife confirmed receipt of the funds, informed her husband, and the defector's brother got money in North Korea, a state where the average income is estimated at just $1,200 a year.
Brokers typically charge up to 30 percent fees for such transactions, but by and large, they work well.
"I heard it only took 15 minutes for my brother to get the money (after funds were wired)," said the defector, who is officially listed as dead in North Korea. "Two days later, my brother called me back saying 'Thank you. We will spend your money wisely'."
The woman is one of the 23,000 defectors living in South Korea, with which the North remains technically at war after an armistice ended the 1950-1953 Korean War.
Some 70 percent send money home to the country they fled, says the Organization for One Korea, a South Korean support and research institute on North Korean defectors. Annual flows are estimated at $10 million a year as defectors try to help out families in a country where many are malnourished and lack access to basic healthcare.