Dark Order. Ryan Weller Thriller Series, #13

An Island Paradise . Hidden Nazi Gold . A Deadly BattlegroundWhen Steve Carlton purchases Big Darby Island in the Exuma Cays so his daughter can build a tropical getaway, he's faced with one disaster after another. Someone wants him to leave his own island and is willing to do whatever it takes to make him. Desperate, Carlton turns to Ryan Weller, whose growing reputation as a troubleshooter has garnered more headlines than he'd like.
He agrees to exorcise the "ghosts" that haunt Big Darby, but when the former EOD tech arrives, the only person he finds is Carlton's daughter Diane, a woman hellbent on restoring a neglected house and to starting a new life. She's not about to be scared off or persuaded to leave, even if it's for her own good. The "ghosts" have their own plans-a methodical search for Nazi gold secreted out of Berlin during the closing days of World War II.
To find it, they'll let nothing-or no one-stand in their way. Forced into hunting for the gold, Ryan finds himself trapped between a relentless adversary intent on installing a Fourth Reich and the desire to save a woman he is desperately trying to distance himself from. But in order to save both their lives, he must first play the deadliest game.