Liz Sansborough is an agent with the CIA.
As you read the first book, you quickly grow to question that statement. An important mystery regarding Sansborough is her identity. Is she an agent trained to hunt down one of the best contract assassins working the political field. Or she is an assassin herself, working with that assassin, named the Carnivore. Or she is a reporter who looks enough like her cousin to be mistaken for her. Each of these is part of the truth behind the puzzle that is Liz Sansborough.
The mystery behind these questions make up the first book as the reader is shown the situation behind the problem and learns along with the characters what the truth really is. The second book does not have that situation but lets the reader follow the main character as she learns to deal with the truth.
Sansborough is the child of agents, two people who were very good at what they did and from whom she learned a lot of her tradecraft, even if she did not know she was learning it at the time. It was only natural that she would go to work with Langley. She had been an agent for several years but grew tired of the violence and wanted out so she left. Just wanting to get out, though, is often not enough especially if the agent is the daughter of the world's best assassin, Hal Sansborough aka the Carnivore, and neither he nor those who he works with nor those he works against is willing to let her go.
She is forced to show everyone that, while she does not like what she has to do, she is very, very good at doing it.