Dr. Sanjay Gupta, NN Chief Medical Correspondent, travels to Cuba to investigate one of the most complex and controversial brain mysteries in recent years, known as Havana Syndrome. First reported by two dozen U.S. officials in Havana, Cuba starting in 2016, these unexplained health incidents have since multiplied to include hundreds of reports of concussion-like injuries around the globe. American officials have yet to make clear what is behind these injuries and whether a directed energy weapon may be to blame.The victims describe suffering from vertigo, headache, brain fog, and in some cases, pain or ringing in the ears without any apparent mechanism of injury. Since 2016, US government officials around the world have reported similar incidents. Investigations by the FBI, the CIA, and the US Department of State have yet to fully explain what happened to these individuals who fell ill while serving their country. The lack of clear answers has led to growing tensions between victims, US lawmakers, and the government agencies investigating these incidents. Critics say these agencies too quickly dismissed these cases despite working theories that a foreign government, or proxy, may have coordinated intentional Cold War-style attacks on American officials using directed energy weapons.Gupta interviews several patients, including a former CIA senior medical officer who traveled to Cuba to investigate the incidences only to fall ill himself and a former Trump official who believes she was injured at the White House. Both are sharing their stories for the first time.Gupta also speaks with Cuba's top scientists and diplomatic officials, who conducted their own investigation and remain skeptical of the reported incidents on their soil. However, prominent US brain experts Dr. Michael Hoffer of the University of Miami and Dr. Douglas Smith, director of the Center for Brain Injury and Repair at the University of Pennsylvania, examined many of the patients and explain why they believe their injuries are very real.But what causes the mysterious illness? Dr. David Relman, who co-authored the influential American Academy of Sciences report, concluded that microwave energy is a plausible explanation. This finding takes Gupta's journey down an eye-opening road into how microwave energy interacts with the brain and what types of directed energy technologies are potentially capable of doing this.