The Sapphire Affair (Jewel #1) by Lauren Blakely

Bounty hunter Jake Harlowe knows how to track a criminal. So when a group of swindled shareholders hire him to trail their former CEO, Jake expects a quick trip to the Cayman Islands to close another case. Until a devastatingly beautiful woman gets in the way.

Steph Anderson is visiting the Caymans for a rock climbing and dive trip—or so she tells Jake. She’s really trying to find out whether or not her stepfather embezzled money from his company. The last thing Steph needs is the distraction of a sexy, charming man whose kisses drive her wild.

Soon, the pair discover they’re after the same target—and millions in jewels. While Jake can’t be certain Steph isn’t working for her stepfather, and Steph can’t be certain Jake isn’t after the diamonds for himself, they can agree the heat between them is intense, and neither can deny the passion for long.

But the morning after, Steph discovers that she just might have slept with the enemy, and now she’ll have to outwit him to get everything she needs…