In the spring of 2013, "The Swiss Machine” Ueli Steck set out to climb Mount Everest and then neighboring Lhotse without oxygen. But he and climbing partner, Simone Moro, ended up in an ugly confrontation with some Sherpas who were fixing lines on the route. The fight spilled into Camp 2, culminating in a group of Sherpas attacking the two European climbers with rocks. In High Tension, Sender Films, which was embedded with Steck, digs into the Everest clash, an incident with an added dimension after an avalanche killed 16 Sherpa guides on April 18, 2014.