Classic Billy Wilder film noir, part scripted by Raymond Chandler and based on the novel by James M. Cain. An insurance salesman, Walter Neff (Fred MacMurray) gets involved in a plot with the wife of one of his clients, Phyllis Dietrichson (Barbara Stanwyck) to kill her husband and claim accident insurance against his death. "Double indemnity" is a clause in the policy that pays out double in certain unlikely scenarios, such as death on a train.
The story is narrated in retrospect by Walter Neff, confessing his involvement by recording a memo to his claims manager Barton Keyes (Edward G. Robinson). The dialogue is snappy and stylized, hard and witty - if delivered a little woodenly, especially by MacMurray.
Neff has a habit of lighting Keyes's cigars for him by flicking a match with his fingers. He smokes heavily himself and has an old-fashioned attitude to "dames" and "babes" and a cock-sure chat-up technique.
The plot is compelling, despite these quaint distractions of mannerism; twisting and wriggling towards the end. Nothing is quite "straight down the line" as Neff keeps saying to Phyllis Dietrichson.
Nugget: what makes this a classic? It's fun and a grand example of its genre. Part of its charm now is that it's dusty and old hat: they don't make 'em like this anymore.