Brest, in 2025 police captain Ludovic Béguin is investigating the death of a woman found drowned on the beach at Corsen. In a virtual reality room to re-study the crime scene captured by drones, Ludovic discovers that he can get in touch with his wife Mélanie, who died on this same beach in 1998. Ludovic then decides to do the impossible, to save the deceased , but altering the past could have serious consequences for the present. For 27 years, Ludovic has rebuilt his life. He has a new wife, Parvana, and a son, Sam...

After discovering that Zoé Levy and Mélanie were wearing the same ring when they died, Ludovic is now certain that they were murdered by the same person. Are there other victims that no one has linked to this case so far? At the same time, Mélanie's changed actions in 1998 have devastating consequences for the future: colleagues and friends do not meet. Their current family simply does not exist. These changes cause Ludovic to panic. What happens if Melanie survives... what will happen to Parvana and Sam then?

Ludovic and Nathan discover that the abusive boyfriend of Nolwenn, the third victim, is the son of a goldsmith from Brest. Could he be the mysterious killer with the ring? Mélanie provokes a meeting with Parvana in 1998, and thus the future changes for Ludovic.

Mélanie is upset when she learns who is most likely the killer. She makes one last request: to meet her daughter, whom she has not seen growing up. In 2025, Ludovic is removed from the investigation. Will he be able, with the help of Mélanie, to prevent the inevitable?...

In 1998, a panicked Mélanie is on the run from both Ludovic and Nathan. She seeks refuge in a place she thinks she is safe, but soon realizes what a mistake she has made, and in a last burst of energy and hope, flees and runs to the beach. Will she be able to escape her terrible fate?...