Once a Thief (Quinn/Thief #1) by Kay Hooper

It had taken centuries for Max Bannister’s family to acquire their treasures, and now he’s been asked to risk his collection as bait for a master criminal. For his own reasons, Max allows a public exhibition, and to protect the family fortune he must rely on the skills of his half brother—a world-class security expert—and his smart and savvy exhibit director, Morgan West.

But almost immediately, Morgan comes face-to-face with the mysterious Quinn, Interpol’s most wanted thief for the past decade—and a man who makes it very clear he has an eye on the Bannister collection. And if that’s not enough, Morgan begins to realize that she’s surrounded by secrets and lies, and that someone very close to Max is moving behind the scenes, intent on murder as well as robbery...someone whose ultimate plan threatens to ruin them all.