As Lucky Luke and his trusty steed Jolly Jumper are finally about to take a few days off, they stumble upon Fanga Town — a city obsessed with jeans, soda, burgers and selfies — thriving thanks to Jeff McDium’s factory. This unscrupulous tycoon monopolizes drinking water and pollutes the river in the name of progress. Only a young and mysterious rebel, with questionable methods, dares to stand up to him. Will she manage to win Luke over to her cause?