OATH BOUND by Rachel Vincent , Unbound trilogy

So this is the last of the Unbound trilogy and in this book, it is the story about Sera. She is the daughter of the head of one of the two head crime Skilled families but she was hidden from the world by her mother. Now her family is dead and she goes to her Skilled (and new boss of her biological father's sindicate) aunt, to ask for a favour. To track and kill her family. Only favours are not that easy to ask and there are a lot of secters that she doesn't know.
On the other side, we have Christopher, Kori's and Kenley's brother, who after trying to help his sisters, one of them is getting kidnapped. And the only place that he thinks she is , is Towers sindicate, where she was bound for years. But after not finding her, he finds Sera. But the most weird thing? He knows he must take Sera with him when he leaves. Because he was told, to take the girl with the yellow scarf.
The last book brings down a lot of bad people lets just say, and a world that excisted for years is finally on its end! And so is the trilogy!