Sans l'orang-outan is in three parts, in the first of which the narrator Albert Moindre (a favourite character for Chevillard, and his surname – 'moindre', meaning 'slightest' or 'least', is a favourite word) – learns that the last two orangutans, Bagus and Mina, have died of a virus. Moindre works in the zoo and everyone is devastated by the news.
The second part goes crazy, and the narrator is plunged into a barren, meaningless, hellish violent world in which almost any hope of humanity, any hope at all in fact, is virtually non-existent. All because the orangutan has gone. This part is very similar in theme and tone to Chevillard's next novel, Choir (2010), and could very easily be viewed as a precursor to it.
The third part, as well as reminding us of the disappearing forests causing the orangutans to lose their habit for the increasing use of palm oil, plunges us into surrealism: Bagus and Mina have been stuffed, and as a reminder of what has been lost Albert Moindre has their remains displayed in a glass case for all to see. There are also very odd remarks that he makes about his sexual attraction to them, which reminds me of Joseph's behaviour in Marie Nimier's La Girafe (1987).
Sans l'orang-outan can be seen as a symbol of impending ecological catastrophe or by extension of humanity's insensitivity to anything other than profit. It is a genuine horror story.