Dragonfly — Tom Lowe

Sean O'Brien knows that his close friend, Dave Collins, isn't a man who asks for favors. After three decades as a CIA officer, Collins learned self-reliance from the best school in the world - the streets. However, after five years out of the agency, he stops looking over his shoulder. 

And then the assassinations begin. 

One by one. Five of the CIA's best former officers. Dave Collins' old colleagues. Local police can't protect retired CIA officers from ghosts of their past. 

Dave's life is on the line, and they are coming for him. Ghosts don't leave tracks. They leave bodies. But to get close enough to kill Collins, they'll have to get through one man who also learned survival from the streets and combat - Sean O'Brien. Dave Collins has been there for O'Brien. 

And now it's time to return the favor.