It's instructive to compare 'The Big Combo' with another detective film, 'Mystery Street', filmed earlier in 1950. Both films were shot by the great cinematographer, John Alton. Where 'Mystery Street' features a cool-headed detective finely played by a young Ricardo Montalban, 'The Big Combo's investigating officer is the hot-headed Lieutenant Leonard Diamond (with a stiff Cornel Wilde miscast in the role). Montalban's detective solves a difficult crime with finesse, always doggedly pursuing one clue after another until he arrives at a solution. In contrast, Wilde's Diamond is clueless from the beginning; he has nothing on Mr. Brown in terms of solid evidence and appears utterly impotent each time he has a face-to-face confrontation with the elusive psychopath.
At the beginning, we find out that Diamond has exceeded the police department's budget for investigating a case with no leads. In terms of today's money, the $18,000 would probably be equal to $180,000 and at the very least Diamond would have been taken off the case for mismanagement of police funds.
Like Mystery Street which featured ahead of its time CSI techniques, 'The Big Combo' tries to prove it too is relevant. The first 'gadget' is a tape recorder which Diamond uses to record his statement to the Commissioner about the funds used in the Brown investigation. That goes nowhere so we're then supposed to be impressed by Diamond's use of a lie detector after Brown agrees to be questioned. Brown's responses to Diamond's questions are hilarious (Question: Women? Brown: Expensive!). But more notable is the stupidity of Diamond's investigation techniques. The only clue he has to go on is 'Alicia'--the name Brown's girlfriend blurts out at the hospital after a suicide try. Is Diamond so stupid to believe that Brown is going to tell him who Alicia is and implicate himself in a murder? What's more Diamond is thoroughly unprofessional when he tells Brown at the hospital that he would like to 'cut him open' as if he were conducting an operation and is afraid to find out "what's inside". Even in the 50s, a loose cannon like Diamond would have been reigned in by his superiors.
During the lie detector test, Brown associates 'Spaghetti' with 'Betinni'. One wonders how the always-in-control Brown could make such a gaffe as it's an important clue that eventually leads to the crime boss's undoing. Betinni, an associate of Brown's former boss, disappeared after a warrant was issued for his arrest. Diamond has no idea where Batinni is, but lo and behold, after being 'tortured' by Brown and his minions and dropped off at his boss's doorstep, Captain Peterson, it turns out that Peterson knew all along where Betinni was hiding. As for the torture (some internet posters have laughably likened it to a scene from Tarrantino's 'Reservoir Dogs), it consists of Brown's use of his underling's hearing aid and a bottle of hair tonic (with 40% alcohol) which he manages to force down Diamond's throat.
Still with no clues, Diamond brings in the 96 suspects in Brown's organization for questioning (funny how Brown's 'organization' really seems to consist only of Joe McClure, the gangster wannabe now demoted to gopher, and two gay thugs, Fante and Mingo (more about that in a minute). Captain Peterson quite rightly blurts out, "Diamond, what am I going to do with you?"
The rest of the Big Combo plot emphasizes Diamond's utter inability to pin anything on Brown. Betinni's tip leads Diamond to antique dealer Nils Dreyer who used to be the captain of the yacht in which Brown and Alicia sailed on. Dreyer is murdered before he can spill any beans but leaves a photo in a bank deposit box, a more recent picture of Alicia. This time the CSI unit gets it right and is able to blow up the Alicia photo, proving that she's living in a sanitarium, only a few hours away. Alicia is about to remember who Brown murdered on the yacht but goes back to the looney bin after Brown shows up and says hello to her. Meanwhile, McClure tries to double cross Brown but Fante and Mingo turn on him and Brown blows him away (one can't forget the scene in which Brown takes out McClure's hearing aid and tells him that at least he "won't hear the bullets".) Finally, Brown double crosses Fante and Mingo by bringing them what looks like a box of money but is actually a stick of dynamite. Mingo is devastated when Fante is killed and agrees to testify against Brown, not for Diamond but for his beloved gay lover (the Big Combo does win points for suggesting that Fante and Mingo are gay which is unusual for a movie from the 1950s). Diamond finally tracks Brown down at an airport (where we never see a single plane) and places him under arrest (amazing how Diamond dodges all those bullets Brown fires at him!).
The Big Combo does have a few good things going for it. In addition to the sensational noirish cinematography, there is an undercurrent of dark sexuality running throughout the film's narrative. In addition to Mingo and Fante's 'different' relationship, Diamond becomes involved with a sexy show girl who ends up murdered on Brown's orders. Brown's girlfriend, Susan Lowell, a former classical pianist, also can't seem to shake off her physical attraction to her gangster boyfriend (despite the fact there is not one scene where the two show any good feelings toward one another).
On the other hand, in addition to the overly moralistic and implausible Lieutenant Diamond, the Big Combo is full of histrionic performances (I love how Brown weakly slaps the prizefighter and McClure flinches as if Brown had slugged the guy, at the film's beginning).
The Big Combo marks the end of the film noir anti-hero. Lieutenant Diamond is more the prototype for Sgt. Jack Friday of TV's Dragnet than Robert Mitchum's femme fatale victim in 'Out of the Past'.