Hi MsLion.
Ok well I'll give you what I remember.
Spoilers for will robie series.
In the first book you learn that robie is an assassin for the cia and his job is to get rid of threats to the united states. He is on a job when he realizes that he is about to kill the wrong target. As he is leaving he rescues a little girl who's parents were just killed by unknown men. Robie and the girl julie hide out until robie is asked by his boss to pose as an fbi agent to see what's going on with these murders. The main fbi agent nicole vance doesn't trust him from the first.
After many more murders and assassination attempts they discover that the whole thing was a plot to assassinate the president. Robie stops the assassination but kills his girlfriend who is the assassin. He is devistated over this and at the end of the book he has to rescue nicole and julie from the remaining conspirators.
In the hit robie is tasked with killing jessica reel who has killed a fellow cia agent. She commits a few more murders and robie learns that all of the dead people were planning to cause an appocalypse. Later robie and reel team up to stop a major assassination of many politicians. They stop it and at the end of the book robie and reel appear to be in a relationship. Robie also visits the girl julie who makes a few appearances in this book but is not a major character.
Hth.