The end of Russia's building boom could cause more problems on Afghanistan's borders.

VOSAY, Tajikistan—Taking a car from Dushanbe, Tajikistan's easy-going capital city, to the Afghanistan border requires special permission from government authorities. I didn't have it. Which was why I found myself near the border in a town called Vosay, drinking tea and cognac with a local man after we had aborted his harebrained plan to take his special "short cut" over the mountains to a string of border hamlets where the Tajik police rarely go.

A half-hour earlier, I had been in a car spinning dangerously over treacherous mountain overhangs on a soft road of loose gravel and dirt. The temperature dropped, and it had begun to drizzle. Cell phone coverage had evaporated, and goats kept getting in our way. At one point, the car skirted both edges of a precipitous drop, and in the fading light we were having more and more close calls on the switchback turns. The local man had gripped his hat and airily observed that the rain could turn the dry river bed crossing the road ahead into a swiftly moving creek. That's when I told the driver to turn around.

Back in Vosay, which had zero electricity and no clean water, women stood around large earthen kilns baking flat bread. Rail-thin children scrambled around ramshackle buildings. A passing sheepherder flung his stick at the legs of laggards in his flock. And at the mouth of the village, a large group of men just stood around.

At first sighting, Vosay appeared to be an innocuous pastoral tableau, impoverished and eerily quiet but a comforting destination after our attempt at the back road to Afghanistan. But for anyone concerned with regional stability and near-term developments in Afghanistan, the scene in Vosay is far more worrying than any broken-down mountain border road. It all starts with those idle men.

Since the start of the war in Afghanistan, the northern alpine border with Tajikistan has been the border that mattered least. True, little Tajikistan (its population is less than 7 million) became a significant conduit for drug trafficking, and a new U.S.-built bridge provides Afghanistan with an important northern trade link, but generally speaking, Tajikistan has been more like a bit player in the Afghanistan conflagration. The real drama was down the road over by the big outside actors in the conflict, Pakistan and Iran.

In the last few weeks, however, Tajikistan has started to play a much bigger role.

The trouble starts at Russian construction sites. Tajikistan derives a full half of its total GDP from remittances, according to International Monetary Fund statistics. Most of this money is earned by Tajik men working jobs generated by Russia's fevered building boom. But the financial crisis is poised to put an end to all that, potentially sending upward of 1 million young, restless, broke, and mostly male Tajiks home to a nation without electricity and bereft of jobs, impoverished and misgoverned, where half the population is under the age of 18. Like sharks returning to an irreparably damaged coral reef, these restive former migrants are heading to a country in an advanced stage of decay.

In every village, town, and city I visited in Tajikistan, there were men standing around. They had returned from Russia to visit their families and wait for the spring construction season to begin.

Many returnees told me they intend to go back to Russia—they had no alternative—but several already had disturbing stories. Among the dozen or so men in Vosay, half said they had been ripped off by their bosses in Russia. They received only a fraction of the money owed to them. One man said relatives had to send money for his train ticket home. Others said they had borrowed money from other Tajiks in Russia. "I would prefer to deal with the skinheads in Russia if I can make money," said a 30-year-old migrant squatting against a piece of junk sheet metal. "What can I do in Tajikistan?"