I saw this when I was 15 or 16. It was part of an anthology series (syndicated?), a gritty film noir-type production set in New York City. Since I saw it probably around 1970, I would guess it was made between 1959 and 1965.
It told the story of a hit man (I would swear he was played by George C. Scott) stalking his victim over the Christmas holidays, narrated in the second person (“You’re like your gun—a well-oiled machine!”). Said assassin encounters an old girlfriend (“Laurie”) and starts going soft and sentimental, to the point where he tells his Mafia handlers he wants out of the hit (“You’re in big trouble for even thinkin’ that!”). When he finds out she’s married, he reverts to his old cold-hearted self, whacking the target inside his own girlfriend’s apartment. Even though he carried out the contract, his handlers rub him out at the payoff, since they believe he can’t be trusted anymore.
I can’t find it in Scott’s filmography or in any Internet search. Does anyone out there recognize it?
Still, it’s a great movie worth seeing. My description really doesn’t do it justice.