Treachery's Devotion. Trinity Masters: Masters Admiralty, #1

A doomed love affair. An unsolved murder. And a mystery a thousand years in the making. Sophia knows how to keep secrets, and how dangerous those secrets can be. Her family's power and position are why people call her the principessa, but that's also why she's tasked with investigating a gruesome crime. Unable to solve the riddles the killer left behind, Sophia reaches out to an expert. Dr. James Rathmann shows up, guarded by modern-day knight Tristan.
Both men are devastatingly sexy, wickedly smart, and deliciously protective. Sophia doesn't need their protection, but the safety she feels when she's with them is all too alluring. When clues reveal that this murder may only be the first of many, they find themselves in a game of cat and mouse and passion is put to the test when the killer sets his sights on the three of them.