In the complex world of international espionage and diplomacy, danger is an accepted part of the job description. For centuries, diplomats and intelligence officers have navigated risks ranging from surveillance and blackmail to political instability and physical threats. These are the known hazards of a profession conducted in the gray spaces between nations. In 2016, however, a new and profoundly unsettling kind of threat began to emerge from the shadows in Havana, Cuba. It was silent, invisible, and it left its victims with inexplicable and debilitating injuries. This was the dawn of a medical and geopolitical mystery that would become known as the Havana Syndrome, a phenomenon that continues to challenge our understanding of modern warfare, technology, and the very vulnerabilities of the human brain.