From the New York Times bestselling author of STAR WARS: BROTHERHOOD.

The only thing harder than finding someone in a time loop is losing them.

Grieving her best friend's recent death, neuroscientist Mariana Pineda is ready to give up everything to start anew. Even her career --- after one last week consulting at a top secret particle accelerator.

Except the strangest thing happens: a man stops her and claims they've met before. Carter Cho knows who she is, why she's mourning and why she's there. And he needs Mariana to remember everything he’s saying.

Because time is about to loop.

In a flash of energy, it’s Monday morning. Again. Together, Mariana and Carter enter an inevitable life, four days at a time, over and over, without permanence except for what they share.

But just as they figure out this new life, everything changes. Because Carter's memories of the time loop are slowly disappearing. And their only chance at happiness is breaking out of the loop --- forever.