Dr. Sanjay Gupta 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. Despite various government investigations, American officials have yet to make clear what is behind these injuries and whether a directed energy weapon may be to blame. Dr. Gupta sets out to explain the truth behind "Havana Syndrome," the extent of its impact on the brain, and the potential continuing threat facing government officials at home and abroad.