If there's one thing that's always bugged me about Double Indemnity, at least in retrospect several years after I last saw it, it was the sense that everything about it was a bit too calculated and the script so sharp that the plot and actor's have no room to believe.  Seeing once again, I was struck by how this utter precision - evident in everything from the cinematography which casts shadows and light in geometric shapes and patterns to the dialogue and performances as carefully mannered and crafted as a sculpture - is crucial in developing the film's sense of inevitabilty, giving it the feeling of a funereal march.  Every piece of dialogue and movement of the camera and actors is designed to mirror Walter's obsessive attention to the minutest details of the plan.  Yet with every move, as carefully and thoroughly thought through, Neff moves another step closer to his own demise, a fate put in action from his very first glimpse at Mrs. Dietrichson's anklet.  Underlying this fate is the dissociation between the perfect plan he hatches in his mind and the real world where it must unfold, most importantly the fact that he must trust Phyllis as well as keep his boss, Keyes, at bay.  This perfect dichotomy between a plan of technical perfection and an imperfect world where such a plan cannot escape the grasp of predestined downfall is what makes the film, at least in some ways, the quintessential film noir.  Wilder and Chandler's screenplay is not simply flaunting its muscles, but creating a vision of haunting despair where Neff, even in carefully sidestepping the traps as they come (the husband at first not taking the train, the stranger from the train coming to the office and Keyes initial hunch that another man helped Phyllis plan the murder), cannot escape the linear death drive once its set in motion.  As Phyllis reminds him later in the film, "It's straight down the line for both of us. Remember?"

Neff, played with equal parts caustic wit and utter desperation by the straight-faced Fred MacMurray, is also the perfect blank slate upon which the drama plays out.  He is a loner with no attachments aside from his job and, even in that, he refuses to settle down to a desk job, preferring to roam the streets, peddling insurance to strangers.  In his first iconic exchange with Phyllis, he mentions that he's learned a lot about the world while doing his job and we get the feeling he didn't like what he saw.  His attraction to Phyllis is at first purely sexual as he first glimpses her half-dressed as she comes in from sunbathing, but it is not in his nature to seek permanence in any form, so it's difficult to believe that he ever thought or even wanted their plan to work out despite the obvious care put into it.  While Neff is ultimately shown to be a means to an end for Phyllis, the same could be said the other way around.  Neff is by nature a drifter - sure, a drifter with a job and the respect of his boss, but still a man with seemingly no desire to conform to the standards of society, at least in the form of settling down with a wife or a job behind a desk.  As an outsider with no real desire to become an "insider", it appears to me as if Neff's sexual attraction, while at first tittilating, ultimately triggers a self-destructive psychosis.  He admits early in the film that Keyes would sniff out a scheme like theirs in no time, yet he follows through with it for the temporary pleasure of having Phyllis.

Phyllis herself is certainly a prototypical femme fatale, but as much as she pushes Neff into the situation, he lays the groundwork and executes it while remaining aware that their is little chance of its success.  His impermanent nature again rears its head twice more later in the film, the first time when he wants Phyllis to keep her distance as Keyes closes in and later when he's instantly willing to let her hang for the crime when he knows Keyes is going to pin it on Phyllis and her secret lover, Nino Zachetti.  Both instances suggest that Neff is far from obsessed from getting the happy ending that Phyllis constantly reminds him of while his final actions, turning Nino away from the house and confessing to the crime before Keyes shows up, ultimately convey his true desire simply to be left alone to die.  The final image isn't haunting so much in its reversal of roles in the lighting of the match, as in the notion that Neff is left to die with the only person who actually cared for him looking at him as if he doesn't exist.  And in some ways, that's what Neff was after all along.