Nick Bianco (Mature) is a small-time New York City hood who can't get a job in the straight world due to his criminal record, and thus is having problems supporting his wife and two small children. So as the film begins, he's returning to a life of crime by robbing a jewelry store on Christmas Eve. Unfortunately he is shot and wounded at the scene and arrested. Assistant DA Louis D'Angelo (Donlevy) offers Nick a deal if he will inform on other crooks, but Nick refuses, content with the mob's offer to take care of his wife and kids while he's in the slammer.
However, Nick finds out while in prison that the mob has completely failed to look after his wife and kids; his broke and despairing wife has killed herself and his children have been sent to an orphanage. Bitter at the betrayal and desperate to get his kids back, Nick belatedly accepts D'Angelo's deal and gets paroled. One of the people he informs on is Tommy Udo (Widmark), a seething psychopath of a villain with a highly unsettling, giggling laugh. Nick is therefore horrified to learn that Udo was acquitted at the same murder trial where Nick testified, and consequently is out free and bent on revenge, putting Nick's life – along with those of his kids, and his new wife Nettie (Colleen Gray) – in dire peril.
Not to be confused with the trope Kiss of Death, which is not featured in this movie.
- Agonizing Stomach Wound: Discussed Trope, as unhinged Tommy Udo says he likes to shoot victims in the stomach to see them suffer.
- Arch-Enemy: Tommy is none too pleased with Nick after Nick testifies against him.
- A Birthday, Not a Break: As Tommy and Nick are being taken away to their separate jail destinations, Tommy remarks that it's his birthday. Then he giggles creepily.
- Bound and Gagged: When Nick and his cronies rob the jewellery store at the start of the film, they leave the clerk bound and gagged. He manages to squirm his way over to the counter and activate the alarm.
- Bury Your Disabled: Poor, poor Mrs. Rizzo...
- Chiaroscuro: An outstanding example of artful black-and-white photography being used to establish mood, like in the scene where Nick waits in a dimly lit house, expecting Tommy to arrive and kill him.
- Establishing Character Moment: Nick's first encounter with Tommy Udo is when they are both in a holding cell waiting to be sentenced for separate crimes. A guard walks by. Tommy, giggling like a schoolboy, talks about how he'd like to stick both thumbs into the guard's eyes and jam them right into his brain.
- Faux Affably Evil: Tommy Udo puts up a friendly facade, but it does nothing to lessen how vile he really is.
- Film Noir: One of the iconic examples, with arty Chiaroscuro lighting, a terrifying villain, disturbing violence, and a tormented hero trying and failing to go straight.
- The Ghost:
- Nick's wife Maria, referred to many times, who kills herself offscreen. This was due to Executive Meddling. Scenes were shot in which Nick's wife commits suicide after she is raped by Rizzo, a gangster who was in on the jewelry heist with Nick. This was deemed too disturbing by censors, so the character of Maria was cut from the film, leaving only an unexplained allusion to Rizzo somehow being responsible for her death.
- Not to mention Pete Rizzo himself.
- Giggling Villain: Tommy and his super-disturbing giggle might be the Trope Codifier for film. He is especially prone to giggling when committing violence, like when he sends an old lady in a wheelchair on a short but exciting trip down the stairs. The character of Tommy is said to have influenced how The Joker is played in various incarnations of Batman. Frank Gorshin stated Udo was his inspiration for The Riddler in the Batman (1966) series.
- Happy Ending: Enforced by Executive Meddling. The original idea had Nick sacrificing himself, tracking Tommy down and basically letting Tommy shoot him so that Tommy would go to jail and Nick's family would be safe. That was deemed too much of a downer, so Nettie's narration tells that Nick survived and lived Happily Ever After with his wife—despite being shot by Tommy five times at close range.
- Medium Awareness: In the very first shot in the opening credits. Said shot is a closeup of the "Shooting Script" of Kiss of Death. The pages of the screenplay then flip by, showing all the credits.
- Mistreatment-Induced Betrayal: Nick initially refuses to squeal, believing the mob would look after his wife and kids, but he changes his mind after finding out that they failed to do so and his wife killed herself.
- Narrator: Nick's second wife, Nettie (Coleen Gray), narrates the beginning and end of the film.
- Non-Indicative Name: As noted above, there is no Kiss of Death in Kiss of Death.
- Orphanage of Love: The orphanage where Nick retrieves his kids seems to be a pretty decent place.
- Police Are Useless: First D'Angelo and the district attorney's office botch the case against Tommy, leading to his acquittal and putting Nick in a very dangerous position. Then the police lose their tail on Tommy, leaving Nick free to come after him.
- Real Stitches for Fake Snitches: Seen in the remake. Ronnie Gannon gets Jimmy Kilmartin re-involved with the car theft racket, leading to his arrest. Then he's indirectly responsible for Jimmy's wife Bev getting killed while Jimmy is inside. Jimmy gets revenge by offering the cops details on an old job he helped pull, coming clean about his own involvement but excluding all mention of Ronnie. When everyone involved is arrested except for Ronnie, their boss Little Junior Brown assumes he's the rat and beats him to death.
- Recycled In Space: The Fiend Who Walked the West was Kiss Of Death as a Western! Future Paramount boss Robert Evans played the "kooky killer" Giggling Villain.
- Sadist: Tommy Udo is very much one of these.
- Sleeping Single: One might think that Nick would want some sex after three years of jail, but he and his new wife Nettie (an acquaintance of Maria's from before Nick went to prison) sleep in separate beds.
- The Sociopath: Tommy Udo has absolutely no regard for human life whatsoever.
- Staircase Tumble: By force. The most famous scene in the movie features a giggling Tommy taking Rizzo's wheelchair-bound mother and pushing her and her chair down a flight of stairs to her death.
- The Stool Pigeon: Nick, although he is a pretty sympathetic example since the mob promised to protect his wife and then failed to do so, leading to her suicide. This cuts no ice with Tommy, who hates the hell out of stoolies.
- To the Pain: Discussed Trope, as Tommy remarks that when he kills people he likes to shoot them in the belly so that they suffer for a while.
- Train-Station Goodbye: An ominous one, as Nick, who is expecting Tommy to come for him at any time, sends Nettie and the kids away.
- Uncomfortable Elevator Moment: Certainly a tension-filled one. Nick and his gang in the opening scene rob a jewelry store that happens to be on an upper floor of a skyscraper. After binding and gagging the workers, they have to take a slooooooooow ride down the elevator, while hoping they can get down and get away before the store clerks work their way free and sound the alarm.
- Would Harm a Senior: Tommy kills Rizzo's old, wheelchair-bound mother by pushing her down a flight of stairs.