In a not-so-distant future where society has changed considerably but the problems often remain the same, a young policewoman from Paris is dragged into a difficult, dangerous investigation that could impact the very future of mankind.

Now attached to French intelligence, Romane is training hard with agent El Malik and Delph, a genetically modified Dolphin with extraordinary mental abilities. The goal of their coming mission: to infiltrate the premises of Algapower, the company at the heart of their investigation, and find clues as to its actual activities – in particular the mysterious Mermaid Project. What is the aim of Algapower’s genetic research? Time is running short...

Roger, Romane’s brother, has been transferred to an Algapower lab in Brazil. Shortly afterwards, his sister, still working for Intelligence, arrives in Rio. Her new mission: to get in touch with her brother and convince him to inform the authorities on the company and its mysterious Mermaid Project. The stakes have changed for the Pennac siblings, though: among the documents retrieved during the New York mission, their names appear on a list of potential test subjects...

Romane Pennac’s niece has been kidnapped in Paris. Her genetic makeup, inherited from the experiments conducted on her mother – and Romane – in her youth, make her a perfect candidate for Algapower’s hybridisation experiments. Hell bent on rescuing her and putting an end to the corporation’s actions, El Malik and Pennac attempt a daring raid on Algapower’s Rio laboratory. But when things go wrong, they’ll find some very strange allies...

Romane and Brahim have reached Algapower’s artificial island, with the help of some cetaceans with a quite extraordinary behaviour. All they need to do now is sneak into the laboratories, locate Romane’s kidnapped niece, and find a way to escape with her before the corporation’s mad scientists transplant a dolphin’s tail onto her. Not an easy task, especially as Algapower’s found some ruthless allies. But the two agents, too, have some rather unexpected allies – and a revolution is coming...