Lawrence Block 
Hit Man 

Keller is a hit man who finds his life turned upside down when a job means more than the one allotted death…Keller is an assassin – he is paid by the job and works for a mysterious man who nominates hits and passes on commissions from elsewhere. Keller goes in, does the job, gets out: usually at a few hours’ notice. Often Keller’s work takes him out of New York to other cities, to pretty provincial towns that almost tempt him into moving to the woods and the lake shores . . . Almost, but not quite.But then a job goes wrong in a way Keller has never imagined and it leaves him with a big problem. Finding himself with an orphan on his hands, Keller’s job begins to interfere with his carefully guarded life. And once you let someone in to your life, they tend to want to know what you do when you’re away. And killing for a living, lucrative though it is, just doesn’t find favour with some folks.