It was a hot afternoon, and I can still remember the smell of honeysuckle all along that street. How could I have known that murder can sometimes smell like honeysuckle? Maybe you would have known, Keyes, the minute she mentioned accident insurance, but I didn't. I felt like a million.
Neff smells the innocuous scent of honeysuckle as he walks down the street. When he compares that smell to the scent of a murder, he is saying that he could never have imagined that such a normal occasion would result in death. He was enjoying his day, naive of any inkling that Keyes was about to ruin everything for him.
"So I let her have it, straight between the eyes. She didn't fool me for a minute, not this time. I knew I had ahold of a red-hot poker, and the time to drop it was before it burned my hand off. I was all twisted up inside and I was still holding on to that red-hot poker. And right then it came over me that I hadn't walked out on anything at all, that the hope was too strong, that this wasn't the end between her and me. It was only the beginning."
Neff uses this extended metaphor to describe the dynamic between him and Phyllis, right after their second meeting. He has just realized that she wants to use him to knock off her husband, and he realizes, too, his own attraction to her, her power over him. He knows he is in a dangerous situation, and that he must "drop" the dangerous thing as quickly as possible—but he also realizes that he may not be able to do so.
"It's just like the first time I came here, isn't it? We were talking about automobile insurance, only you were thinking about murder. And I was thinking about that anklet."
In their last meeting—before they both die at each other's hands—Neff finds himself in the same situation with Phyllis as he was when he first met her, except he's not innocent this time. The first time he had no idea of Phyllis' intentions for him. While he was thinking that she was wealthy and pretty, he had no suspicion that she saw him as an opportunity to rid herself of her husband. Now as the two face off once more where they first met, Neff feels that he finally has the upper hand. He's accomplished things and learned, but Phyllis is exactly the same as she was before and thus at a disadvantage.
"So we just sat there, and she started crying softly like the rain on the window. And we didn't say anything. Maybe she had stopped thinking about it, but I hadn't. I couldn't because it was all tied up with something I'd been thinking about for years. Since long before I ever ran into Phyllis Dietrichson. Because, you know how it is Keyes, in this business you can't sleep for trying to figure out all the tricks they could pull on you. You're like the guy behind the roulette wheel, watching the customers to make sure they don't crook the house. And then one night, you get to thinking how you could crook the house yourself. And do it smart. Because you've got that wheel right under your hands. You know every notch in it by heart. And you figure all you need is a plant out front, a shill to put down the bet. And suddenly the doorbell rings and the whole setup is right there in the room with ya."
Here Neff describes to Keyes, his boss in the insurance business, how he came to justify his crime to himself. Having spent his life trying to prevent others from taking advantage of insurance companies, he has developed a skeptical, paranoid vision of humanity. At a certain point, he started to think that he could use this knowledge gained from monitoring others to beat the system himself. Since you're screwing or being screwed, when an opportunity presents itself to turn the tables, Neff jumps at it. This is how he describes his fateful meeting with Phyllis.
"It's got to be perfect, understand. Straight down the line."
Walter is the first character to utter this line, which significantly repeats over the course of the film. Phyllis repeats it back to him initially, and later repeats it to him after he gets Mr. Dietrichson to sign the accident insurance policy: "It's going to be a train, Walter. Just the way you say. Straight down the line." The line refers to a number of things: first, the fact that the plan must be faultless; second, the fact that the plan takes place on a train, literally traveling down a railway line to Palo Alto; third, the fact that the two are now bound together, imprisoned even, by the undertaking of the plot.
"There's a speed limit in this state, Mr. Neff. Forty-five miles an hour."
Phyllis and Walter's first meeting is an ironic reversal of the dynamic between them that will eventually play out, with Walter playing the role of predator in their first encounter. Phyllis uses this line to chastise Walter's untoward advances, turning to a motor vehicle metaphor that later anticipates the train metaphors ("straight down the line") used to describe their plot together.
"I think you're rotten."
Phyllis says this to Walter during their second meeting, when he quickly intuits her plan to have Mr. Dietrichson killed and collect on his accident insurance policy. Walter later repeats it back to her, calling her "rotten" in the penultimate scene of the film, before she finally shoots him.
"A claims man, Walter, is a doctor and a blood-hound and a cop and a judge and a jury and a father confessor, all in one."
Barton recites this line as part of his sales pitch to Walter to become his assistant as a claims man, but Walter refuses. Walter still admires Barton due to his genuine passion for the job, which Barton describes in the style of a great rhetorician.
"Look, Gorlopis. Every month hundreds of claims come to this desk. Some of them are phonies, and I know which ones. How do I know, Gorlopis? Because my little man tells me."
Barton's "little man" speech reveals the gnawing sense of discontentment that drives his efforts as claims investigator. Barton describes it to a man named Gorlopis as a kind of indigestion, and it later strikes him again when he is working on the Dietrichson case.
"I love you, too."
Walter says this line twice to Barton, the second time being the final line of the film. The first time, Walter says it as a kind of joke in response to Barton's grumpiness. The second time seems to be a sincere expression of affection for the man to whom he felt most intimate, and with whom he shared a much more pure, loving bond than the one he tried to build with Phyllis Dietrichson.