After about an hour's climb, we rest by a boulder under some prayer flags, while behind us, two waterfalls tumble down from the hillside. Shortly after, we meet our first Indian trekkers. Vishal from Patna is accompanying his friend down to Phortse Thanga. She fell sick from altitude in Machhermo, and cannot descend alone. “Wahaan scenery to jannat hai yaar,” he tells me, “but be careful. Lots of people are falling sick.” His friend gives us a wry smile, and then they disappear down the trail.