On a chilling Friday night in April 1968, amidst the bustling streets of Chicago, mobster Johnny Ross briefly reunites with his brother, Pete, after narrowly evading a horde of gunmen outside his office. Their meeting in the garage of their building is fleeting, filled with brotherly exchanges, before Pete contacts his mob superiors to report Johnny's escape.
Fast forward to Saturday afternoon in San Francisco, where a curious man inquires about any messages for "Johnny Ross" at a hotel, visibly taken aback by the absence of a response. After making some calls, this man reveals himself to be an ambitious politician named Walter Chalmers (Robert Vaughn), who is striving to bolster his political image by aiding the Senate subcommittee hearing aimed at exposing organized crime, particularly targeting Pete Ross ([Vic Tayback]). Bullitt unfolds over the span of this critical weekend, capturing the intrigue and tension leading up to the much-anticipated hearing.
Due to the high stakes involved, Johnny Ross is placed under the protective custody of the San Francisco Police Department for the weekend after embezzling $2 million in mob funds from Chicago. Lieutenant Frank Bullitt (Steve McQueen), along with Sergeant Delgetti (Don Gordon) and Detective Carl Stanton (Carl Reindel), provide round-the-clock surveillance at the Hotel Daniels, a rundown establishment located near the Embarcadero Freeway. Lieutenant Bullitt organizes a three-shift rotation, first assigning Delgetti, followed by Stanton, and then himself.
However, in the dead of night, while Stanton converses with Bullitt over the phone regarding Chalmers’ impending visit, Ross stealthily unlocks the door. In that moment, a pair of merciless hitmen invade the room, resulting in a chaotic shootout that leaves both Stanton and Ross critically injured.
Driven to uncover the truth behind the violent ambush, Bullitt pursues an investigation that runs counter to Chalmers' insistence on placing the blame on the police force. A mysterious elderly man, later identified as the shotgun killer, seeks information about Ross at the hospital, setting in motion a chase as Bullitt attempts to apprehend him—only to have the assailant slip through his fingers.
Amidst the chaos, Ross succumbs to his injuries, compelling Bullitt to conceal the news of his death, instructing Doctor Willard (Georg Stanford Brown) to misclassify the body as a John Doe. The hearing pressure mounts as Chalmers demands answers from Bullitt, who remains impenetrable.
As the investigation unfolds, Bullitt discovers that Ross' presence in San Francisco is tied to his previous heist from the Chicago Outfit. Questioning the hotel desk clerk—who was rendered unconscious during the ambush—yields vital information on the cab Ross had taken.
Bullitt confronts the cab driver, Weissberg (Robert Duvall), who divulges that Ross had made crucial phone calls prior to his arrival at the hotel. This leads Bullitt on a high-octane pursuit through the vibrant streets of San Francisco as he engages in a bone-chilling car chase with the assassins, culminating in a fiery crash that eliminates the threats.
As Bullitt diligently follows clues, he learns of a murderous setup involving the Rennicks, leading to more entanglements with Chalmers, who strives to manipulate the unfolding events for his gain. When Ross is revealed to have taken a flight to London under yet another alias, Bullitt races against time, confronting Chalmers and defying his machinations.
In a gripping climax at the San Francisco Airport, Bullitt's final chase concludes with a shootout that leaves Johnny Ross lifeless and Chalmers empty-handed. Upon returning home to find Cathy (Jacqueline Bisset) waiting for him in bed, Bullitt is left to face the unsettling reality of his life choices, pondering the darkness that looms over his profession as he gazes into the mirror, questioning if he has indeed become what he feared.
