In France in the year 1700, a skilled and eager swordsman named Lagardère (Daniel Auteuil) challenges Duke Philippe de Nevers (Vincent Perez) to a friendly duel in order to learn his secret lethal trick known as the "Botte de Nevers". Nevers agrees and quickly wins. Nevers then learns that he has a child by Blanche de Caylus, a fact previously concealed by his cousin and would-be heir, the wicked Count of Gonzague (Fabrice Luchini), who's deeply jealous of him and has an unrequited love for Blanche.
That night Nevers escapes an assassination attempt by Gonzague's men, who paid a naive Lagardère to join them. Lagardère refuses to kill Nevers, and the latter spares his life, hiring him as trusted companion on the road to Caylus for his marriage, teaching him his lethal trick. Gonzague has all the Caylus wedding's guests slaughtered and stabs Nevers in the back, leaving Nevers' baby girl Aurore orphan and heir to his wealth, and it's up to Lagardère to raise and protect her and avenge Nevers.
Two other notable theatrical film versions of the novel were made, one in 1944 starring Pierre Blanchar and one in 1959, Le Bossu, starring Jean Marais. Television saw a two-part miniseries in 2003, titled Lagardère and starring Bruno Wolkowitch.
On Guard provides examples of:
- Aluminum Christmas Trees: According to sources from the time, there really was a hunchback living in Paris financial district during Philippe d'Orléans' regency, and he really made a living by getting paid to allow people to sign papers on his twisted back (exploiting a superstition saying it brings good luck). His real identity and fate are a mystery.
- Badass Boast: As in all of the book's adaptations, Lagardère throws one to Gonzague: "Si tu ne viens pas à Lagardère, Lagardère ira à toi!" ("If you don't come to Lagardère, Lagardère will come to you!").
- Best Served Cold: It takes sixteen years to Lagardère to avenge Nevers, clear his own name and give Nevers' stolen wealth and titles back to Aurore.
- The Cavalier Years: The film is set at the very beginning of the 18th century, which saw the end of King Louis XIV's reign and Philippe d'Orléans' Regency.
- Calling Your Attacks: Rare, justified example. Aurore is by no means a trained fencer, so when she's facing Louis-Joseph, she recites from memory every step of the lethal technique she was taught, further adding to the confusion of her opponent.
- Collector of the Strange: Gonzague is always assisted by a hunchback (working as his head accountant) and his dragon is suffering from unspecified deformity, making him look like a burn victim. This is how eventually Lagardère gets close to him - after the first hunchback gets accidently killed, Gonzague organizes a casting for replacement.
- Combat Pragmatist:
- Aside his iconic, flashy moves, Nevers isn't above fighting dirty or throwing a dagger at a guy he can't reach with his sword.
- Lagardère doesn't really care about being stylish or honourable - he goes for a kill or quick "win" during training duels. Even if the latter means offending the Duke of Orléans in the process.
- Louis-Joseph is a big, strong guy. He punches, kicks and throws people around when fighting.
- Confusion Fu: Aurore fights a little randomly when she's pitted against Gonzague's best swordsman Louis-Joseph. It eventually works in her favor, as she is suddenly in a situation that allows her to perform the lethal trick from her father that Lagardère taught her.
- The Cynic: Gonzague is oozing with misanthropic remarks about nobility, common people, investors into his company...
- The Dandy: Nevers chases both fashion trends and ladies.
- Defeat Means Friendship: Lagardère was part of a bunch of hired swords send to assassinate Nevers. Since he's more interested in the duke's fencing technique rather than the payment for the job and Nevers recognises him from earlier once he easily overpowers Lagardère, he offers him a new deal. Rather than trying to kill him, Lagardère will escort him to his wife-to-be and maybe learn something on the way. Not only the men bond quickly over their short stint together, Lagardère shows Undying Loyalty by spending sixteen years on avenging Nevers.
- Dirty Coward: Gonzague is a Non-Action Big Bad and a such does everything he can to avoid direct confrontation with Lagardère when he is eventually cornered. When faced with no other choice, he takes Aurore as Human Shield with a knife on her throat and fights dirty against Lagardère, not being a fencer.
- Faking the Dead: Lagardère fakes his death and that of baby Aurore with the help of an Italian travelling theatre troupe after escaping the massacre at Caylus.
- A Handful for an Eye: Gonzague throws dirt in Lagardère's face to distract him during the final fight. Aurore instead tells him where Gonzague is and eventually uses her own voice as a beacon for Lagardère.
- Historical Domain Character: The Regent Philippe II, Duke of Orléans, is the only historical character to appear in the film.
- Green-Eyed Monster: Gonzague envies Nevers his title, his wealth, his looks and the affection of Blanche (along with Blanche herself), never stopping to scheme against his cousin, as he's the direct inheritor of all his possessions.
- Master Swordsman: Nevers is one of the best swordsmen in the kingdom when the story starts (hence why his cousin prefers stabbing him In the Back, seeing how useless his mooks are against him), and Lagardère wants to learn from him. Lagardère himself has become this through Cocardasse's teachings, and needs only a few more tricks, the Botte de Nevers especially.
- Nasty Party: The guests of Nevers' and Blanche's wedding (including Blanche's father) are all killed by Gonzague and his men.
- Obfuscating Disability: As in all versions, upon returning to Paris with Aurore, Lagardère disguises himself as a hideous hunchback to gain Gonzague's trust and successfully infiltrate his household, hence the title according to a superstitious belief in France at the time, touching a hunchback's back is supposed to make you lucky. Daniel Auteuil's face makeup was far less complex than that of Jean Marais in the 1959 version, consisting simply in a fake nose and a wig, necessitating much less time to prepare for the filming.
- Only One Name: Lagardère is a noble in pretty much all of the other versions of Le Bossu (the minor nobility title of Chevalier, translating as "Knight") and has a full name in them, Henri de Lagardère. Here he is just called "Lagardère", as he is not a noble when the story starts.
- Overprotective Dad: Lagardère grows very protective towards Aurore (his de facto adoptive daughter), as he swore to protect her to her dying father.
- Right Under Their Noses: While organising a manhunt after Lagardère, Gonzague in the same time invites him into his house and makes him his book-keeper, all thanks to a crafty disguise of a hunchback. He's visibly shocked when the charade comes down in the finale.
- Scars Are Forever: While Lagardère never saw the face of Nevers' killer, he branded his left hand. Not only Gonzague wears a glove on that hand for the rest of the story to conceal the mark, it is eventually used as a proof he's the killer of Nevers in the end.
- Servile Snarker: For as long as Nevers is alive, Gonzague never stops to be in the same time always at his service (especially when it comes to the duke's wealth), while constantly being one step away from openly berating him. Nevers is too naive to notice.
- Signature Move: The Botte de Nevers fencing trick, which results in the enemy being impaled on the forehead between the eyes if well executed. Nevers passes it onto Lagardère, who later teaches it to Aurore.
- Sore Loser: The Duke of Orléans visits the fencing school of Cocardasse and Passepoil where Lagardère trains at the beginning and gets offered a new sword by Nevers. He insists on duelling someone, and Lagardère volunteers. The Duke is older and Lagardère makes sure not to hurt him, but then he charges foolishly, slips and collapses on the ground, causing some hilarity among the fencing pupils. The Duke gets up and gets annoyed, and insists that he slipped because of a "macaroon".
- Street Urchin: This version of Lagardère wasn't noble by birth, he grew up in the streets.
- Trial by Combat: Duke of Orléans decides to make the duel between Lagardère and Gonzague into one of those. Gonzague is quick to point out that God always seem to stand on the side of the stronger and better swordsman.
- Waif-Fu: Subverted. When Aurore faces Louis-Joseph, he constantly takes advantage of being bigger, heavier and stronger than her, quite literally throwing her around and easily keeping her at distance.
- Why Won't You Die?: Invoked few times by various characters toward Lagardère, as he always seems to end up dead, only to show up again few days later and wreak even more havoc. Gonzague eventually asks one of his assistant what did he do to Lagardère that he refuses to just die after being apparently drown, stabbed, shot and stabbed again, always coming back.
- Widowed at the Wedding: Blanche de Caylus, as Philippe de Nevers gets killed the very morning after their wedding.