Tess is a part of the mafia. Not just any part, though, she's godfather. The Boss. And people think that because she's a girl, she can't kick their ass. In fact, her identity is kept secret so they don't seem weak.
So imagine Damon's supprise when he finds out that the King of the Mafia is actually a girl. Not to mention that she's the heir to his rival mafia. However, he's determined to destroy them. Even if it means allying with their heir.
The question is will she help him? Will she betray her uncle? Or will she be the ruthless heir she was born to be? How far is Damon willing to go to destroy the ones that destroyed his family? Will he betray Tess in the end simply because she is related to them? Or will he want to keep her close when he finds out about her past that lead her to be the King of the Mafia?