It is 1845, and Anthony Hope, a young sailor, has just arrived home to London. He is accompanied by a man he rescued drowning off the coast of Australia, Sweeney Todd. As they disembark, they are accosted by a beggar woman who alternates between begging for alms and soliciting sex, but seems to recognize Sweeney.
Anthony is thrilled to have returned to London, but Sweeney is not—he tells Anthony the tale of a young barber who was sent into exile by a powerful man with designs on the barber’s beautiful wife. Sweeney enters a pie shop on Fleet Street, and is immediately confronted by the owner Mrs. Lovett. She bemoans the hard times and the scarcity of meat (and the speedy cats). Sweeney asks about the empty apartment upstairs. Mrs. Lovett tells him about the barber Benjamin Barker who was falsely accused by Judge Turpin so that the Judge could get Barker’s wife, Lucy. The judge and Beadle Bamford lured Lucy to the judge’s house so he could torment and rape her. Sweeney’s anger confirms what Mrs. Lovett had suspected–that he is indeed Benjamin Barker.
Mrs. Lovett tells Sweeney that Lucy poisoned herself, and that his daughter, Johanna, was now a ward of Judge Turpin. Mrs. Lovett returns a set of silver shaving razors to Sweeney, who vows to use them to get his revenge. In Judge Turpin’s house, Johanna sits at a window. Anthony happens to wander by and immediately falls in love with the beautiful young woman. Threats from the Beadle only strengthen his resolve to save her.
Barber Signor Pirelli’s assistant Tobias Ragg hawks a miracle elixir that regrows hair. After exposing the elixir as a hoax, Sweeney challenges Pirelli to a shaving contest, which Sweeney wins easily. The Beadle judged the contest and is impressed—Sweeney invites him to come in for a complimentary shave. Anthony, not knowing that Johanna is Sweeney’s daughter, asks the barber for help—he intends to rescue Johanna, and wants to use the shop as a safe house. Pirelli arrives to pay Sweeney a visit. Mrs. Lovett takes Tobias downstairs for a pie, and Pirelli drops the accent and reveals that he used to be Benjamin Barker’s assistant. Instead of giving in to blackmail, Sweeney kills Pirelli.
Johanna is terrified because the judge intends to marry her on Monday, but Anthony has a plan to help her escape. Meanwhile, the Beadle suggests that the judge clean up a bit to be more attractive to Johanna, and sends him to Sweeney. As the judge tells Sweeney about his impending marriage, Sweeney shaves him, enjoying the anticipation of his revenge. But before he can slit the judge’s throat, Anthony bursts in and blurts out his plan to save Johanna. The judge storms out, declaring that he will lock Johanna up and never come to the barber shop again. Sweeney swears to kill as many people as possible, punishing the rich and corrupt and freeing the poor from their saddened state. Mrs. Lovett sees an opportunity—they can dispose of the bodies by using the meat for her pies—and so a new enterprise is born.
Mrs. Lovett’s pie shop is now bustling, and Tobias helps with customers. Sweeney has a brand new chair, with some special modifications. When Anthony discovers that the judge has locked up Johanna in the asylum, he gets Sweeney to help him plan an escape—Anthony will go to the asylum pretending to be a wigmaker looking for hair from the inmates. Seeing an opportunity to lure the judge back to his shop, Sweeney writes a letter, warning him of Anthony’s plan, and that Anthony and Johanna could be captured at the barber shop.
Tobias has begun to suspect that there is something awry at the pie shop, and tries to warn Mrs. Lovett. Mrs. Lovett distracts him and sends him down into the bakehouse. She returns upstairs to find the Beadle waiting—he has been sent to investigate the strange smells and smoke coming from her chimneys. Sweeney comes in and offers the Beadle his free shave. Tobias is still in the basement when the Beadle’s body tumbles down, and he runs off.
The asylum owner Jonas Fogg tries to stop Anthony from rescuing Johanna. She shoots Fogg, leaving the rest of the inmates to wander through the streets of London, as Sweeney and Mrs. Lovett search for Tobias. Back at Sweeney’s shop, Johanna hides to avoid the beggar woman, and Anthony goes looking for Sweeney. When Sweeney arrives and finds the beggar woman in his parlor, he slits her throat. The judge arrives, and Sweeney lures him into the chair before revealing his true identity and killing the judge. Johanna comes out of hiding and barely escapes Sweeney’s knife.
Mrs. Lovett struggles with the bodies in the basement. Sweeney arrives, and in the oven’s light finally recognizes the beggar woman—it is his wife Lucy. Mrs. Lovett only let him assume that the poison killed his wife out of love, and Sweeney takes Mrs. Lovett in his arms for a dance, but then shoves her into the oven.
Sweeney kneels on the floor, holding Lucy. From behind him, a white-haired Tobias approaches and slits Todd’s throat just as Johanna, Anthony, and the police enter.