Complex sentence: Mysterious deaths begin to occur in the small town near the base, and postmortems reveal that the brains and spinal cords of the victims are missing, but the locals become convinced that fallout from radiation at the base is causing the deaths.
Split into simpler sentences: Mysterious deaths begin to occur in the small town near the base, and postmortems reveal that the victims' brains and spinal cords have disappeared. The locals become convinced that fallout from radiation at the base is causing the deaths.