North Korean leader Kim Jong Un shocked the world last month when he accused his uncle and mentor of treason and had Jang Song Thaek executed.
The consequences of that purge are reaching beyond North Korea's border. Jang had been in charge of trade with China, and his death has had a chilling effect on ties with North Korea's neighbor and longtime ally.
Nowhere is that being felt more acutely than in China's northeast, where Chinese freight trains rumble across a bridge over the Yalu River and into North Korea. This corner of the country is just about North Korea's only point of contact with the outside world.
To many Chinese, the place is a rust belt.
But to the few North Koreans lucky enough to make it, a visit there can be a mind-expanding experience.
One 58-year-old woman who came to visit her relatives says that on her first visit to China, the affluence and abundance she saw dazzled her. She and the other North Koreans NPR interviewed requested anonymity so as to avoid severe punishment back home.
"What I found here was unimaginable. So much food here is wasted. The roads, the cars, the electricity. It's always bright, whether it's night or day. I wondered, where is all this electricity produced? In North Korea, it's very dark at night, you can't do anything and it's very lonely," she says. "Even If you tell people, it sounds like a dream. They won't listen to you, or they'll wonder if you're telling the truth."
But in North Korea, she says, it's dangerous to talk too much about her experiences in China.
So when she returns home, she says she takes the amazement and envy she felt and hides them in her heart.
A signal to China
On Monday, citizens in Pyongyang marched through the streets, pledging support for policies outlined by Kim Jong Un in a New Year's address.
In the speech, Kim said that the purge of his uncle had strengthened the unity of the ruling Worker's Party.
In addition to charges of treason, Jang was accused of selling North Korean resources, such as coal, to China cheaply.
Clearly, on one level, Jang's purge was an internal power struggle.
But Cai Jian, a Korea expert at Fudan University in Shanghai, says that it was also, in part, a swipe at China.
"Jang's purge," he says, "reflects the fact that North Korea does not want to see China wield excessive political or economic influence over it, and the purge may be a move to weaken China's control and influence."
Cai says that for the moment, the purge may appear to have helped Kim consolidate his rule, but it also reveals a split over economic policies.
The toll of political tensions
Back at the border, one former North Korean truck driver, who asked that NPR disguise his voice in addition to not naming him, says that North Koreans are angry that the coal they use to heat their homes became more expensive as coal exports to China increased.
"Jang should have sold the leftover coal that our people don't use. He's a bad person. How could a good person sell coal to China for a few cents when North Koreans are freezing in their homes?" the man says. "The people think that it's right that he died."
A North Korean woman who works in a Chinese department store, who also asked for her voice to be altered, says that political tensions appear to have taken a toll on border trade in recent months.
"There are fewer North Korean customers buying Chinese goods and there are fewer products going into North Korea," she says. "But I didn't notice any other changes. After all, how could North Korea survive without trade with China?"
The former truck driver says there's still a market for Chinese goods because there's nothing else to buy.
"The North Korean economy is now paralyzed. There are no government factories left working. Metal and coal mines, factories which earn foreign exchange, and those that make soybean paste and other food stuffs – those are the only ones left running."
Fudan University's Cai says that Chinese find North Korea's hereditary Kim dynasty rather anachronistic.
But they have decided that the stability of the Kim regime is in China's strategic interest, so they will continue to support it at all costs.