Conger, the protagonist, is given a chance to get out of jail if he agrees to travel back in time and kill a man. He has agreed to kill a stranger he has never seen. He isn't concerned about getting the wrong man. He knows what the man looked like. There was no way he could make a mistake about his target's identity -- he has the man's skull under his shoulder.
Sandry's Book
Marooned in Realtime
Starman
Gravity Rising (The Parallel Multiverse Book 2)
Tales of the Vuduri: Year Two
Housing Problem
Tatja Grimm's World
And Shall Machines Surrender