Scylla by Chris Berry

In Greek mythology, Scylla was a multi-headed monster who lived above the Strait of Messina. Travelers passing through the narrow channel faced an impossible choice: steer close to Scylla's rock and die to her snapping jaws, or veer toward the whirlpool Charybdis and risk being swallowed whole. There was no safe passage. There was only the choice between two ways to die.

A year after surviving Charybdis, Diane Wallace and Charlie Bradon are still in the strait.

Branded as rogue agents. Hunted by the system they served. They have spent twelve months chasing a name whispered by a dying man, a name that leads nowhere. Dead ends. Cold trails. A case eating Diane alive. A lead takes them from Italian villas to the mountain town of Davos, where the world's elite gather to decide the world's future. Diane is captured, broken, delivered to a private island that doesn't exist on any map.

The island, a place of opulence and revelry, of beautiful people dancing under champagne lights, a paradise built for those who worship at the altar of excess. But behind the curtains, behind the marble and the palms, something monstrous lurks. And Charlie is coming to bring her home.

What comes next is not a rescue. He's collecting the butcher's bill.