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Mobster Carmine Ricca (Richard Devon) drives away from court and an angry mob after being acquitted on a technicality. An SFPD motorcycle cop stops Riccaâs limo for a minor traffic violation. Suddenly, the patrolman pulls his service revolver, shoots all four men in the car, and rides away.
Inspector Harry Callahan (Clint Eastwood) and his partner Earlington "Early" Smith (Felton Perry) visit the crime scene, despite being on Stakeout duty. Callahan's superior, Lieutenant Neil Briggs (Hal Holbrook) dismisses them, seeing Callahan and his tactics as reckless and dangerous. Callahan in turn quips, "A man's got to know his limitations," mocking Briggs's pride in not ever drawing his gun in the line of duty. Callahan and Early then stumble upon a hijacking attempt at the airport; Callahan poses as a pilot to thwart the two would-be terrorists.
Rookie cops Phil Sweet (Tim Matheson), John Davis (David Soul), Alan "Red" Astrachan (Kip Niven), and Mike Grimes (Robert Urich) encounter Callahan at an indoor firing range. Sweet, after demonstrating his speed and accuracy with Callahan's gun, reveals that he is an ex-Airborne Ranger and Special Forces veteran and that the others are as good or better shots than himself. The young officers' zeal and marksmanship impress Callahan.
Later, a motorcycle cop slaughters a mobster's pool party using a satchel charge and a sub-machine gun. Shortly afterwards, a pimp (Albert Popwell) who murdered one of his prostitutes (Margaret Avery) is shot dead by another motorcycle officer. Callahan realizes that the pimp had let his killer approach him and offered a bribe. He deduces that a cop is likely responsible, and suspects his old friend Charlie McCoy (Mitchell Ryan), who has become despondent and suicidal after leaving his wife, Carol (Christine White).
Another motorcycle cop murders drug kingpin Lou Guzman (Clifford A. Pellow) and associates using a Colt Python equipped with a suppressor. However, Guzman is under surveillance and Callahan's old partner, Frank DiGiorgio (John Mitchum), sees McCoy dump his bike outside Guzman's apartment complex just before the murders. The motorcycle cop encounters McCoy in the parking garage and kills him to eliminate a potential witness. Harry presents his suspicions about McCoy to Briggs, who informs him of McCoy's death.
At the annual combat pistol championship, a puzzled DeGeorgio tells Callahan that Davis was the first officer to arrive after the murders of Guzman and McCoy. As Davis proceeds to break Callahan's speed and accuracy records, Callahan borrows Davis' Colt Python and purposely embeds a slug in a range wall. That night he retrieves the slug, and ballistics reveals that it matches those found at the Guzman and McCoy crime scenes. Harry begins to suspect that a secret death squad within the department is responsible for the murders.
Briggs ignores Callahan's suspicions and insists that mob killer Frank Palancio (Tony Giorgio) is behind the deaths. When Briggs obtains a warrant for Palancio's arrest and tells Harry to lead the raid, Callahan requests Davis and Sweet as backup. Palancio and his gang are tipped off via a phone call and arm themselves; in the ensuing gunfight Sweet is killed, along with Palancio and all his men. A search of Palancio's offices turns up nothing that would incriminate him, raising Harry's suspicions further.
The three remaining renegade cops confront Callahan in his garage complex. They present Callahan with a veiled ultimatum to join their organization: "Either you're for us or you're against us." He responds, "Iâm afraid you've misjudged me." While checking his mailbox, Harry discovers a bomb left by the vigilantes and manages to defuse it, but a second bomb kills Early as Harry phones to warn him.
Callahan summons Briggs and shows him the bomb. While driving to City Hall, Briggs suddenly draws his revolver and forces Harry to disarm, revealing himself as the leader of the death squad. He cites the traditions of frontier justice and summary executions, and expresses disappointment for Callahan's refusal to join his squad. Grimes appears behind the car, following along as backup.
Callahan distracts Briggs by sideswiping a bus and beats him unconscious. Grimes gives chase and shoots out the car's rear windshield before Harry manages to run him over. The two remaining motorcycle cops appear and Callahan flees onto an old aircraft carrier in a shipbreaker's yard. As they stalk Callahan through the darkened ship, Astrachan shoots recklessly and runs out of ammunition, allowing Callahan to ambush and beat him to death. Callahan runs onto the top deck and starts up Astachan's motorcycle, leading Davis in a series of jumps between ships before the two run out of deck space. Callahan manages to skid to a stop, but Davis falls to his death.
Callahan makes his way back to the car, but a bloodied Briggs appears, intending to prosecute him for killing the vigilante police officers rather than just shoot him dead. As Callahan backs away from the car, he surreptitiously activates the timer on the mail bomb and tosses it in the back seat. Briggs is driving away when the car explodes, killing him. "Man's got to know his limitations", Callahan quips again, before walking away.
Deleted scenes[edit]
Cut from the final film were two scenes that elaborate on Harry's suspicions of the rookie motorcycle cops.[citation needed]

The first scene cut takes place before the combat pistol championship and after Davis and Harry watch McCoy's funeral flight take off. Harry and Davis drive from the airport to a bowling alley for a few drinks and a black youth is chased outside and assaulted by four toughs. Davis attacks the toughs while Harry dispatches one with his beer mug. After subduing the robbers, Davis harangues a group of eyewitnesses for letting such crimes take place. Harry witnesses this and sees in it his own approach to crime fighting, albeit far more severe.
Later, after examining the bullet from Davis's gun he fired into the wall, Harry checks on old issues of a police magazine. He finds articles condemning the revolving door justice allowed by liberal politics - most of which are authored by the four rookie cops.
Who demonstrates his speed and accuracy with Callahan's gun?
Sweet