Callum Tremaine has spent six years running. After discovering his father's art empire was built on stolen cultural treasures, he stole a 500-year-old Moorish map and vanished, spending half a decade hunting hidden vaults across Europe, returning priceless artifacts to the institutions they were taken from, and making sure no one learned his real name.

Then the FBI sends Special Agent Maddox Langley to bring him in.

Maddox is methodical, relentless, and everything Callum has trained himself to avoid. But when the map reveals a vault hidden deep in the Sierra Nevada mountains and Callum's ruthless brother closes in to reclaim what was stolen, the fugitive and the federal agent are forced into a partnership neither of them wanted.

What they find underground will change everything. What's building between them might be even more dangerous.