It's 1927 and we meet silent movie star George Valentin (Jean Dujardin) on top of the world. He's behind the screen; in front of it an ecstatic audience is enthralled by his latest starring role. As the credits roll, Valentin takes the stage for what a virtuosic display of bowing, his canine sidekick performing some cute tricks too.
Outside the theatre, adoring fans and press push and surge to breathe the same air as their hero. A pretty young girl at the front of the crowd drops her wallet, and makes the most of picking it up to slip under the security cordon. There's silence as Valentin looks shocked, confused, angry even - but it's all his joke and, laughing at his own power to create such confusion, he gamely poses for photos with the young lady to the delight of the assembled press, and to the chagrin of his stern, world-weary wife who reads of the escapade in the papers the next day.
The young girl - one Peppy Miller (Bérénice Bejo), we learn - having shared a moment with her hero is inspired to follow his path, and turns up at the studio to audition, successfully, as an extra. Valentin himself arrives at the same studio where he is again the star, this time of 'A German Affair'. On entering the studio the star is enthralled by a pair of legs he sees rehearsing on the other side of a screen. He joins the dance from his side of the screen, and beckons to the set builders to remove the screen, hoping to surprise the girl. It's he, though, who is surprised to discover the legs belong to the same Peppy Miller from last night's crowd and this morning's papers.
Years pass, one presumes in a similar fashion. One day though, Al Zimmer, the immaculately stereotyped cigar-chomping, braces-pinging studio boss (John Goodman) calls Valentin in to see the latest technological innovation - a primitive attempt to record sound with motion pictures. Valentin scoffs at the footage, but is clearly ruffled by it. He dreams a nightmare where everyday sounds are exaggerated (for the first time here the film takes on a diegetic soundtrack) culminating in a confusing cacophony where a feather lands with a boom. Only his own voice is stifled; despite the soundscape around him, he is mute.
Valentin's instinctive suspicion of the technology proves well-founded, when he - once the king of the silent movie - is quickly marginalised, and eventually fired by Zimmer. Audiences want change, he's told. It's time to move on.
Devastated by his sudden fall to insignificance, Valentin takes to drink. Peppy, meanwhile, has done well out of the new 'talkies'. Now the doyenne of the Hollywood set and as wealthy a pin-up herself as her mentor once was, she gives a radio interview in a café in which she attributes her success to the simple truth that audiences want change. "Out with the old, in with the new," she quips. From an adjacent table, unseen, Valentin listens in before theatrically 'making way' for young Peppy, dramatically taking his leave.
Valentin's circumstances go from bad to worse. A self-funded attempt to make a return to the era of silent film ("Tears of Love") flops, and the rest of his savings are wiped out by the 1929 stock market crash. When the whisky runs dry, the ex-star auctions off everything he owns. His dour wife leaves him (perhaps the one bit of good fortune he has enjoyed since the days of stardom) and he is forces to sack his loyal butler Clifton. Finally, in a climax of drunken rage, Valentin sets fire to his old film reels, and, with them, his apartment. Attempting to save one canister in a sudden moment of regret, he is overcome by fumes, and it is only thanks to the endeavours of his ever-loyal dog that he is rescued by a nearby fireman.
Peppy has discreetly been following Valentin's fortunes and is shocked to learn of the fire from the newspaper. She leaves a shoot to visit him in hospital, and, stopping short of declaring her love for him, takes him to her grand villa to recover. Waking briefly, Valentin realises his luck and the pair embrace.
However, while Peppy is out at a shoot, the convalescent Valentin roams the villa, and discovers to his horror a room full of the very possessions he himself had previously auctioned off. His pride deeply wounded by her having come to his rescue without his knowledge, he flees the house and returns to the embers of his burned-out apartment to root out his old pistol. Returning home and realising Valentin has left in anger, Peppy gives chase in her car, guessing his intention.
Valentin sits in his chair with the gun in his mouth, the dog frantically pulls at his trouser leg.
The intertitle flashes up: "Bang!"
But it is outside that we find the source of the noise; Peppy has crashed her car into a tree. She leaps from the wreckage and consoles Valentin just in time to avert catastrophe. She tells him she has secured a role for him in her next production. Valentin is sceptical, saying the audience doesn't want to hear him talk. Peppy tells him she has another idea, and the film ends with the Al Zimmer toasting the next entertainment sensation as Valentin is back in the studio, and back to his ebullient self with Peppy as his tap dancing partner. The consummate artist, Valentin has found a way to use the new sound-recording technology without lowering himself to a speaking part.