I realize it's not Graham Greene, but I really liked this clever novella about Katla, an assassin, who poses as a representative of LKE Enterprises, a company that for a large fee will rid you permanently of people you don't like or upon whom you wish retribution. Katla pulls a multi-faceted con in this novella, available for free for your Kindle.
Hired to kill a former employee who stole a microchip containing some very special and unique programming that will make weapons more difficult to track, Katla figures out a way to shift blame for the eventual killing while retrieving the microchip in such a way that .... You'll just have to read it to find out. Cunning. I intend to read all of Halm's books..
Marred only by a couple of editing errors, e.g. "there" instead of "their," but generally well edited.