In August of 1962, France is in a state of turmoil. President Charles de Gaulle had granted the country of Algeria independence, a decision that has enraged many French citizens. Many of them, mostly fanatics and extremists from the army, have formed an underground organization called the Organisation de l'armée secrète, and one faction, headed by Jean-Marie Bastien-Thiery, decide to assassinate de Gaulle. They set up shop along a road that de Gaulle's motorcade will be taking to Orly Airport, and, as the motorcade passes, open fire on the Presidential car with automatic rifles. A number of bullets shatter and enter the vehicle, but not a single of them make a mark on de Gaulle or anyone else inside. Bastien-Thiery and the other conspirators in the plot are quickly tracked down and arrested. Six months later, Bastien-Thiery's lawyer makes a stay of execution, but it is turned down, and the next morning, Bastien-Thiery is executed by firing squad.
The top members of the OAS, Colonel Marc Rodin, manager Casson and treasurer Montclair take stock from hiding at a remote chalet in the Austrian Alps, and realize that they cannot make any move as they will constantly be watched and identified: the OAS is planted with snitches who will watch every members move, and each member has had their complete details archived. Rodin realizes that what they need is to once again try to assassinate de Gaulle, but this time by hiring a foreigner, someone whom the French authorities have no records of.
Three months later, Rodin eventually finds the right individual, an Englishman with a short but impeccable record. He invites him to Vienna for an interview by the three OAS leaders. The Englishman is smart, enigmatic and cold-blooded; he figures out their need for an outsider to assassinate de Gaulle, given the failed prior attempts and the OAS being riddled with informants. He accepts the job, but warns that he'll have to be paid $500,000 for the work, as anyone who does something like this will never be able to work again. He demands utmost secrecy and anonymity, and asks that no one but the four of them know of this project and that he work completely by himself. He takes the codename "the Jackal", and takes his leave of the OAS heads; his farewell is observed by Rodin's bodyguard and adjutant Victor Wolenski.
To raise money to pay the Jackal, the OAS heads order their network to rob a bunch of banks across France. The tactics range from late night burglaries to daylight ambushes of armored cars. This sudden crime wave is noticed by the French Action Service (the French espionage branch), and although several of the robbers are arrested, they are hired thugs who only know that their bosses have been ordered to carry out these robberies on behalf of the OAS. Their suspicions are heightened when they learn that Rodin and his associates have suddenly secluded themselves in the Hotel Garibaldi in Rome, which is owned by an OAS sympathizer. From research by surveillance teams in the area, they observe that Rodin and co. are untouchable. They live alone on the top floor of the hotel, and the floor below that is occupied by their eight bodyguards, highlighting the mens' fear of being kidnapped. And their only form of contact with the outside world is Wolenski, who makes twice-daily trips to the post office to send and receive letters.
The Jackal begins his preparations: he researches extensively on his target, he acquires two false passports, he pays a visit to Paris to acquire a good shooting location, and he contacts two individuals in Genoa. One is an armorer whom he commissions to build a special rifle; the other is a forger from whom he requires special French documents.
Later on, the Jackal receives an OAS contact named Valmy that will inform him of any developments regarding the President. Around the same time, the OAS sends a female agent named Denise to bed a high-ranking French politician. Two weeks after visiting the armorer and forger, he returns to acquire his purchases. He is satisfied with the gun the armorer has made, and a trial of the rifle goes well; the forger on the other hand tries to blackmail him over his papers, and the Jackal snaps his neck. All his plans complete, he leaves for France under the name of Paul Oliver Duggan.
Meanwhile, as August begins, the Action Service get tired of waiting and decide to have Wolenski taken in for questioning. They abduct him off the street while he's walking to the post office to pick up mail, load him into the back of a truck and drive him to an airfield, where he's then flown to Paris in a small propeller plane. They interrogate and torture him to death, but all they get is that a blond killer named Jackal visited his superiors. This is enough for the chief of the Action Service to conclude that the OAS are employing an outside contract killer as part of a plot to assassinate de Gaulle.
The French Interior Minister asks for an interview with de Gaulle, but his demand for secrecy is rebuffed; de Gaulle is a proud man who refuses to go into hiding or shield himself. The Interior Minister instead convenes a secret council to deal with the Jackal, which includes high-ranking individuals like Police Commissioner Berthier and Colonel St. Clair. Berthier states that because of the Jackal's anonymity from even his own employers, no one has a clue where to start looking for him; the key to finding and stopping the Jackal thus is to establish his identity. He recommends his own deputy commissioner, Claude Lebel, as the best detective in France and ideal for the job of uncovering the Jackal.
Lebel, a mild-mannered but tenacious policeman, is summoned to the council. He is given access to every resource available, but he is asked to keep things secret, and that he succeeds. Lebel brings in his assistant Caron to help him out, and the two get to work contacting the heads of police agencies abroad. Meanwhile, St. Clair arrives home and pours out everything about the situation to his mistress, Denise. She later slips off and phones Valmy...
Over in London, inquiries are being headed by Inspector Thomas, who has been given express authority by the Prime Minister to make full investigations regarding the Jackal (ensuring that he not be English, or if he is to be stopped). The British police come up with two things that they pass over to Lebel. Firstly, that there was a suspicious character named Charles Harold Calthrop who was in the Dominican Republic around the time its dictator Trujillo was assassinated (Jackal in French is "chacal", the word formed from the first three letters of each name); a search on Calthrop's home reveals he is absent. Second and more worryingly, a review of all passport applications reveals that one was made for one Paul Oliver Duggan, who had died at the age of two.
Meanwhile, the Jackal learns from Valmy that his assignment is blown, but decides to continue on regardless. He makes it to a hotel at Grasse, where he spends the night charming and seducing a fellow guest, Baroness Collette de Montpellier.
The next morning the hotel records are taken and scanned, as is French customs (and more urgently than usual). Presently Duggan's name is spotted and immediately Lebel orders forces on the hotel and he heads over there himself. They find no sign of the Jackal, him having already left the hotel (something Lebel finds strange), but they learn that the Baroness's bed had been slept in by two people. Lebel interviews the Baroness, but she denies knowing a thing about the man.
The Jackal's quick getaway before the police arrive is cut short by accidentally crashing his car. He decides to head for the Baroness's estate, where she takes him in. That night she tells him the police were looking for him, but promises she won't say anything if he tells her what he's about; in response, he strangles her. He takes on a new disguise and identity of bespectacled Danish pastor Per Lundqvist, whose passport he'd stolen at London Heathrow Airport, and quickly but quietly leaves. He heads to Tulle station in the Baroness's car and catches a train to Paris. Hours later, the servants discover the Baroness's body.
Lebel reports the failure of catching the Jackal and the murder of Madame de Montpellier, and notes that he could not have escaped unless he had been forewarned and that he now has the identity of a Danish pastor (having traced the car to the station and questioned the station authorities). He also notes that the murder means he can do away with secrecy and initiate a public manhunt. A police squad heads to the railway station in Paris to intercept the Jackal, but they arrive a few minutes too late. Lebel sends police to check every hotel in Paris, but the Jackal evades them by entering a Turkish bathhouse and being picked up by a French homosexual.
Lebel uses a phone tap to discern that Denise is the OAS spy that's been tipping off the Jackal. He presents a recording of her phone call to the council, and St. Clair leaves (he later overdoses on sleeping pills); he'd tapped all the phones of the council members, having had suspicions about the Jackal being forewarned. Afterwards, he works out that the Jackal will strike in two days, or August 25, 1963 which is Liberation Day, the anniversary of France's liberation from Nazi Germany. de Gaulle, as a World War II veteran, is guaranteed to make a public appearance on that day no matter what the threat, and the council disbands, intending to make all attempts to find the Jackal before then.
Meanwhile, the Jackal kills the homosexual when he sees a public broadcast about Per Lundqvist being wanted for murder.
In the early hours of Liberation Day, the Minister wearily informs Lebel that they've been unable to find the Jackal. All they can do is implement the utmost security precautions around. The day goes on, but nothing happens. Some time later, a gendarme allows the Jackal, disguised as an old one-legged French war veteran, to head to his residential address, after seeing his papers; the Jackal enters his location, sheds his disguise and disassembles his crutch to form his rifle, and waits for the President to present medals to former French Resistance members.
Lebel strolls around looking for anything the least suspicious or out of place, but he doesn't find anything until he meets the gendarme around the time the President presents medals. He learns that the officer let a cripple with a crutch through, sees that the address pointed out has a window open on the top floor, and rushes over there, ordering the officer to follow him.
The Jackal aims, takes his shot... and misses because de Gaulle suddenly bends his head to kiss a Resistance soldier on the cheeks, as is French custom. The Jackal reloads his gun for a second shot, but then Lebel and the gendarme burst in on him. He guns down the gendarme, but Lebel snatches up the officers submachine gun and empties it into the Jackal.
Over in London, Charles Calthrop appears at his flat. The British authorities take him in for questioning, but conclude that he had nothing at all to do with the Jackal and close the matter (also forswearing any responsibility regarding the Jackal, since he used a British passport but also the passports of a Dane and a Frenchman). Thomas ponders who the Jackal really was...
The film ends with a quiet funeral in Paris, as the Jackal's body is buried in an unmarked grave, with Lebel the only witness.
