The Lead Masks Case (Brazil, 1966)

Two electronics repairmen are found dead on a hilltop near Rio de Janeiro, dressed in suits and raincoats, wearing lead eye masks. Beside them: an empty water bottle, two towels, and a notebook with cryptic instructions that read "16:30 be at the specified location. 18:30 swallow capsules. After effect protect metals wait for mask signal." No drugs were found in their system, and the cause of death remains unknown. Their bizarre deaths sparked theories ranging from UFO cults to Cold War espionage.