A disturbing cloud has appeared from the west. It moves slowly towards the centre of the country, prompting the population to take to the roads. As it advances relentlessly, panic increases. It is a cloud of acid.

During the summer, Jules, 10 years old, is welcomed by a young couple in the countryside, because his mother had an accident. How to feel at home in a village where its inhabitants are shaken by deep antagonisms. How not to fear what's behind « Les Hautes Herbes », the tall grass?