Creation Lake by Rachel Kushner

Seductive and cunning American spy-for-hire Sadie Smith has been sent by her mysterious but powerful employers to a remote corner of France.

Her mission: to infiltrate a commune of radical eco-activists influenced by the beliefs of an enigmatic elder, Bruno Lacombe, who has rejected civilisation, lives in a Neanderthal cave, and believes the path to enlightenment is a return to primitivism.