The depletion of Earth's ozone layer and the increase of solar radiation as a result of this causes all of the animals in the world that live above an altitude of 5,000 feet to become insane and start killing people due to overexposure to the solar radiation, which is very unfortunate for a group of hikers who have been dropped off up into the mountains by helicopter for a days-long nature hike just before a quarantine in the mountain village that they started from is announced.