Exotic animal species imported into France are multiplying, often to the detriment of native fauna. Examples include rainbow trout damaging Pyrenean lakes, blue crabs overrunning the Étang de Berre, and the decline of European mink whose habitats have been taken over by invasive American mink. Who brought these creatures in? Hugo Clément tracks down the culprits and meets activists fighting to ban the sale of potentially problematic species and to manage released exotic animals.