Jack O'Brien is an American veteran of the Vietnam war, who has become a pillar of the community in Bangkok, where he owns and operates an exotic travel business. A husband and wife team of French scientists asks him to guide them on a hunt for a rare plant in a remote and dangerous part of northern Burma. Initially his concerns about safety cause him to decline, but then 'extenuating circumstances' cause him to change his mind, and assemble a group of former colleagues. Everyone proceeds up the Mekong river and into the jungle, where they encounter native tribes, and confront ghosts from their collective past.