Une théorie prétend que si l'on pouvait retourner dans le passé et changer quelques détails de notre vie, tout ce qui en découle serait modifié. On appelle cela «l'effet papillon». Evan Treborn a cette faculté. Fasciné, il va d'abord mettre ce don au service de ceux dont les vies ont été brisées dans leur enfance.
A mathematical genius discovers a link between numbers and reality, and thus believes he can predict the future.
In Seattle, detective Quentin Conners is unfairly suspended and his partner Jason York leaves the police force after a tragic shooting on Pearl Street Bridge, when the hostage and the criminal die. During a bank heist with a hostage situation, Conners is assigned in charge of the operation with the rookie Shane Dekker as his partner. The thieves, lead by Lorenz, apparently do not steal a penny from the bank. While chasing the gangsters, the police team disclose that they planted a virus in the system, stealing one billion dollars from the different accounts, using the principle of the Chaos Theory. Further, they find that Lorenz is killing his accomplices.
Chaos theory has a bad name, conjuring up images of unpredictable weather, economic crashes and science gone wrong. But there is a fascinating and hidden side to Chaos, one that scientists are only now beginning to understand. It turns out that chaos theory answers a question that mankind has asked for millennia - how did we get here?