This remarkable documentary follows what it describes as 'the highest and most perilous of the world's ancient routes': the Tea Horse Road, established more than 2,000 years ago, which originates in the Nu River valley in Yunnan and crosses the Hangduan Mountains into Tibet, Nepal, Bhutan and India. The tea, carried by caravans of pack-mules, ultimately found its way to the West. Tian and a skeleton crew travel the part of the route which lies within China's present borders, following a caravan which now carries building materials for the 'development' drive. They start in Yunnan and climb to the Tibetan Plateau, pausing to talk to local people (none of whom are Han Chinese) as they go. The journey takes them through landscapes of craggy beauty, of course, but the people give the film its core: they talk about everything from their memories of the tea trade to personal and political misfortunes. (It wouldn't be a Tian Zhuangzhuang film if the Cultural Revolution didn't get a ritual kicking.) The film superbly records social and topographical realities which will soon be gone; it takes its title from the name of one pack mule which means 'Angel of Peace' in Tibetan.