National Geographic photojournalist Steve Winter has spent his life working to save endangered big cats through his award-winning pictures. Now he turns his lens on an elusive and deadly leopard. In Mission Critical: Leopards at the Door, Winter explores Sanjay Gandhi National Park in Mumbai and Corbett National Park in northern India to capture extraordinary footage of leopards living in close proximity to humans — and to tell the stories of a broad array of people whose lives have been forever changed by encounters with the elusive big cats.