Under My Skin by Elizabeth Branson

Mattia “Matty” Lorenzo is cool, calculating, and absolutely certain that nothing will ever drag him back into the life after his fiancé was murdered ten years ago. But when the alluring younger sister of an old friend ends up in the crosshairs of New York gangsters bent on revenge, all Matty’s certainties go out the window. Soon there’s only one thing he knows for sure – there’s nothing he won’t do to keep Fiona Doyle safe.
Fiona Doyle is the baby of the unruly Doyle family. She’s brave, reckless, and dead set on proving that she’s just as tough as her older brothers. She doesn’t want or need a man’s protection. But when Fiona, her brother, and his friend Mattia are faced with a dangerous interrogation, Matty doesn’t wait to ask what Fiona wants before fleeing the city with her in tow.
In hiding, Fiona and Mattia find white-hot attraction and a fragile trust. But when danger comes knocking, their feelings for one another are put to the test. Past tragedy and lies could be their undoing. But if they fight together, they just might survive.