Viktor Moisa, a retired rocket scientist, welcomed the North Koreans to his institute in eastern Ukraine just as he would with any other guests. He took them upstairs to the showroom of Soviet satellites and rocket engines, the pride of the institute’s collection. Then they went out to the yard, where an array of parts for ballistic missiles were on display. This was in the early 2000s, well before North Korea would test its first nuclear bomb in 2006. So the visitors’ interest in missile technology did not arouse Moisa’s suspicion. “They came as tourists,” he told TIME on a breezy afternoon last fall. “At least that’s how they presented themselves.” Continue reading.