When the team of marine biologist Sofia Assalas tried to take bio samples from an anomalously grown mako shark with tag No. 7, the animal grew angry and tore apart the entire group. Three years later, eco-activist Mika comes to Sofia and says that the same individual No. 7 has incredibly adapted to life in freshwater and swum up the Seine. After checking her instruments, the scientist, with astonishment, discovers that this is true, and while she tries to convince the police of this, Mika and other activists decide not to let the shark be killed and to release it into the sea.