The story coheres around the suicide of a crooked cop, and the subsequent struggle of an honest detective, Dave Bannion (Glenn Ford), to navigate between a corrupt city government and a ruthless mobster to uncover the truth. Initially, the violence here seems almost timid by comparison to the more explicit carnage now commonplace in films, yet the story accelerates as its plot arcs toward Bannion's showdown with kingpin Lagana (Alexander Scourby) and his psychotic henchman, the sadistic Vince Stone, given an indelible nastiness by Lee Marvin. When Bannion's wife is killed by a car bomb intended for the detective, both the hero and the story go ballistic: suspended from the force, he embarks on a crusade of revenge that suggests a template for Charles Bronson's Death Wish films, each step pushing Lagana and Stone toward a showdown. Bodies drop, dominoes tumbled by the escalating war between the obsessed Bannion and his increasingly vicious adversaries.
Lang's disciplined visual design and the performances (especially those of Ford, Marvin, Jeanette Nolan as the dead cop's scheming widow, and Gloria Grahame as Marvin's girlfriend) enable the film to transcend formula, as do several memorable action scenes--when an enraged Marvin hurls scalding coffee at the feisty Debby (Grahame), we're both shattered by the violence of his attack, and aware that he's shifted the balance of power. --Sam Sutherland
But is Lang retelling the story of what happened in Germany, or is he warning his adopted country what could happen if people didn't challenge authority (here the police department, including the commissioner) that had been corrupted by a criminal leader? Maybe both.
The Big Heat is violent even compared to today's films and more believable than most. However one thing that jars today is the effeminacy of the crime boss, Mike Lagana, used as shorthand to show his corruption.
We first see Lagana in bed in silk pajamas with his bodyguard (in his robe) standing over Lagana, handing him the phone, lighting his cigarette. When Dave Bannion (Glenn Ford), the homicide detective who won't follow orders and leave Lagana alone, barges into Lagana's mansion to confront him about a cop's suicide, Lagana is under a huge portrait of his dead mother ("We lived together in this house"). Even from beyond the grave you can feel the mother's unhealthy influence on her son. Lagana mentions his daughter but never his wife.
For the most part you can tell the criminals from the decent people because the criminals dress better. Gloria Grahame's Debby Marsh, girlfriend of the vicious killer Vince Stone (Lee Marvin), tells the blackmailing wife of a policeman who was on the take, "We're sisters under the mink."
Debby and the cop's wife are just one pair of doubles in the movie. There's also Debby and Katie, Dave Bannion's wife. (Katie playfully suggests Dave tell his friends she's an heiress. Later, trying to explain why she's with Vince, Debby asks Bannion, "You think I was born an heiress?") Another set of doubles is Lagana's gang and the group of veterans Bannion's brother-in-law gets to protect Bannion's little girl. One vet (described as a poet by one of his friends) shows Bannion his gun and says anyone who comes through the door for the girl is dead. The poet transformed by war (definitely a non-WASP) says he's seen things you can only see from a tank, and starts to say he was one of the first into - - What? Auschwitz? Vince and the hoods playing poker in his penthouse enjoy violence for its own sake. The vets will only use violence if necessary to protect the innocent. But the vets are playing poker too, and seem to relish the prospect of taking revenge on Bannion's enemies, who haven't done anything to them. Between good and evil there are differences but also similarities.
Bannion goes to Victory auto repair, looking for a "mechanic," an explosives expert. The owner says he can't help ("I got a wife and kids, too") but a crippled woman who works as a secretary tells Bannion what he needs to know. Bannion stands outside the auto yard, talking through the fence. Inside the compound the limping woman is just another of the unfit, the "life undeserving of life" tortured and exterminated in other camps, and in camps that exist today.
When Bannion tells the crooked cop's wife, "The city's being strangled by a gang of thieves," she smiles and says, "The coming years are going to be just fine." Just the way things looked in the thirties if you weren't one of those inside the camps.
"Thief" is the strongest epithet Bannion uses. Not "killer" or "murderer." The criminals and the politicians who go along with them are stealing his city. Though people don't like hearing what Bannion has to say, they're lucky he won't quit fighting the murderers among us.