Assassin's Apprentice Falling for the Target

She sits at the top of the hit list, the highest-ranked woman in the trade, and she is getting out. Before she can retire there is one more job, and it is not a killing. A mafia boss has an illegitimate child who is going to inherit, and someone has to turn that child into a person capable of holding the position. She takes the contract and moves in close. The work runs long, the obstacles come from inside the family and outside it, and the two of them get through them together rather than separately, which is not how she has ever worked before. Along the way the assignment stops being an assignment to her.