It's been 18 years since novelist Terry Pratchett made a life-changing journey to the jungles of Borneo. Tonight, he's back among the orangutans to find out what the future holds for them, and discovers that there's a new threat that could push them close to extinction. Terry's trip is rather different this time around though, as his battle with Alzheimer's presents a new physical and mental challenge. Terry considers the role of mankind in the eradication of animal species, and his journey leads him to consider his own mortality.