This Stays Between Us by Sara Ochs

Ten years ago
A study abroad program like no other: a month-long trip of education and adventure, exploring everything Australia has to offer. And at first, it’s everything best friends Phoebe and Claire, and the rest of the student group expects: sunshine, whirlwind romance, and all-night parties. But it isn’t long before cracks begin to form within the group. Ones that lead to Phoebe’s disappearance …

Now
It’s the call Claire has been waiting for years for. Phoebe’s remains have been found. It’s time to return, for her and the others to go back to Australia. But as Claire retraces their steps and tries to piece together exactly what happened to her best friend all those years ago, it quickly becomes clear everyone in the group has secrets. Including Claire.

Because only she knows what really happened that fateful day ten years ago. The day she killed her best friend. And she’ll do anything she can to keep the others from learning the truth.