When a surgeon is murdered in a hospital on December 31, his ex-wife, best friend and an officer find themselves stuck in the same elevator.

On February 9, a month after going back in time, the trio have no clue about the identity of Marc's assassin.

In May 2023, despite the trio's efforts, the year continues to repeat itself. Marc's patients at the hospital are murdered, and they have no leads on the identity of the killer.

Anna, Juliette and Cédric identify Marc's killer. They put a plan in place to catch him but fail to take into account the intelligence and skill of a man willing to do anything.