In 1998, wildlife enthusiast and photographer Chris Packham had a remarkable encounter with the Orang Rimba, a tribe of hunter-gatherers in the rainforests of Sumatra, Indonesia. It was the first time he had ever seen people living in perfect harmony with their environment. One photograph in particular that Chris took, a picture of a young tribal girl, has since become immensely important to him as a barometer of how we are treating our planet. In this real-life detective story, with no clues as to her identity or whereabouts other than his original photograph, Chris sets off to Sumatra 20 years on to try to find her, the girl in the picture.