Anyone understand "Le Samourai"? (really good film, SPERLERS within)

Particularly the last 20 minutes or so.

So Jeff catches the guy that shot him at the money exchange. Before leaving him tied up, the guy offered him one more contract, which the viewer never hears the specifics of. Jeff goes to kill the guy that hired him (which obviously wasn't the unheard contract). He goes to the guys house and, before killing him, finds out it's the same home where he met the hot black piano player. Then, most likely knowing that the cops would be there, he goes to her club to act like he was going to kill her, getting himself killed in the process.

So WTF? Was the black chick the unheard contract and he just couldn't go through with it? I've read about this whole samurai code where they can't turn down contracts, but aside from the title of the film, there is no implication that he adheres to those rules.