Even without the framing device, Billy Wilder's and Raymond Chandler's screenplay would be without reservation in how it quickly telegraphs the story being told. A murder plot slowly heats up and quickly boils over. Nothing will be as realistically smooth as it seems to be for the characters involved. Something will go wrong. We don't need the essentially spoiler-proof intro of a wounded Walter Neff crawling into his office confessing into a dictaphone to tell us as much.

This isn't a criticism but strictly part of what makes DOUBLE INDEMNITY timeless, not merely for helping set foundations for what Film Noir would become but for how Wilder and Chandler use the plot's predictability and framing to maintain laser focus on the several details of the story that, without Wilder's effortless hand, might have erupted into something more convoluted than it needed to be.

Neff's and Phyllis's motivations for getting involved with the central crime are perfectly in sync yet in sharp contrast. Neff's impulsivity clouds him from figuring out--until, of course, it's too late--just how carefully Phyllis planned things out when (not should) things go south.

The twisty narrative finds its grounding in Edward G. Robinson's Barton Keyes. Robinson did very little, perhaps besides showing up, to command attention in any project he was in and that magnifies his presence in this film. His character is key (I'm sorry) to the dramatic irony that maintains our investment into the suspense. Keyes's "you don't need proof if you have instinct" methodology (which is also ultimately offset by the plot's revelations) always keeps him on top of what is going on, his actions so meticulously planned to the point that a running gag (where he always finds himself searching his pockets for matches to light his cigars) actually ends on his own logical punchline/explanation.