In the final seconds before the Pointe Reason nuclear reactor explodes around them in October 1971, Dr. Cecilia Ribold makes a conscious choice: to defy death itself. She, her true love Mitch, and her best friend and fellow physicist Dawn-her platonic soulmate-have a theory about harnessing the laws of physics to direct their own reincarnations. Energy cannot be destroyed, so they devise a method to ensure their bond won't be either. They vow to find each other across lifetimes.

Now, half a century later, they are each fully entrenched in their subsequent lives. Ceclia, now known as Vienna, finds Mitch, now Marcello, in a fateful encounter. Hoping to express her agonizing love for him, while also sending a warning to a culprit she partly blames for the Pointe Reason disaster, she publishes a novel containing details no one could possibly know about the meltdown-unless they'd been there. The novel attracts her old friend Dawn, now Darcey, but also the dangerous attention of the perpetrators of the original disaster and the government who sees directed reincarnation as a valuable weapon. Their lives converge once more in an international chase across continents to defend their love, so deep and unbreakable, it's subatomic.