In the 1960s, a covert operation to install a nuclear-powered surveillance device in the Himalayas went awry when a severe blizzard forced the mission team to abandon the device on an ice shelf. The device, containing a generator with plutonium-238 and plutonium-239, was intended to operate undetected for years. When the team returned months later, the device had vanished, raising concerns about its potential environmental impact. Today, the lost generator poses a lingering threat to the region, potentially endangering hundreds of millions of people who rely on the Himalayan watershed.