Ciel Phantomhive is awakened by his butler, Sebastian Michaelis, who informs Ciel that Damian, the head of one of his factories, is coming for a visit. Sebastian orders the household staff, Baldroy, the cook, Finnian, the gardener, and Mey-Rin, the maid, to prepare for Damian's arrival. However, their attempts result in disaster, as Baldo overcooks the food, Finnian kills the garden by spraying herbicides on it, and Mey-Rin breaks all of the china. To resolve the situation, Sebastian orders them to rearrange the yard into a stone Japanese garden and has Bard make beef tataki. Damian, impressed with the staff's preparations, plays a board game with Ciel in which his character loses his legs and is ultimately incinerated. Following the dinner, Damian calls his associate, commenting that the factory he owns has been sold and he is attempting to fraudulently acquire more money from Ciel. When Damian attempts to return to the lounge, the scenario in the game occurs in real life, as he breaks one of his legs, and Sebastian locks him in the oven, to be burned with the dessert. He later runs away from the mansion.

Ciel is kidnapped for ransom, but Sebastian easily defeats a mob of underlings, with various kitchen supplies, and retrieves his master.

Elizabeth, Ciel's fiancee, arrives at the Phantomhive Estate for a visit. While Ciel does not wish to dance with her, Sebastian convinces him to learn to dance for the sake of preserving his social reputation, and teaches him a simple waltz. Later, Elizabeth is unhappy with Ciel wearing his own ring in favour of the one she has brought him, and she breaks Ciel's ring by throwing it on the floor. Ciel comes close to hitting Elizabeth but is stopped by Sebastian, who explains to Elizabeth that Ciel's ring is the Phantomhive family's ring. Elizabeth is upset, but Ciel throws the ring out of the window and declares that he is the head of the Phantomhive family, with or without it. Ciel then wipes Elizabeth's tears away and dances with her. That night, Sebastian finds Ciel depressed in bed and produces Ciel's ring, undamaged. Ciel wonders how many Phantomhives have died wearing the ring. He tells Sebastian to stay by his side until he falls asleep, amusing Sebastian and causing him to comment on Ciel showing his weaknesses to him.

The news of Jack the Ripper terrorizes the city of London. Sebastian narrows the suspects down to a single man, a Viscount. Madame Red creates a plan for Sebastian, Ciel and Lau to attend a ball to catch the culprit, which involves Ciel wearing a dress and Sebastian pretending to be his tutor. They realise that Elizabeth is attending the ball and dance across the ballroom to avoid her because she would then blow there cover and then they would get caught.As Ciel says that Elizabeth has too much energy. The Viscount takes a liking to Ciel, who attempts to seduce him, while Sebastian distracts Elizabeth and the other guests by pretending to be a magician and gets trapped in a box with all these knifes and chains with using only magic as he says(which is true). Alone in a room with the Viscount, which turns out has a smell that Ciel thinks its just a smell,then Ciel loses consciousness, later awaking to find himself being sold in a large underground auction, tied and blindfolded. When the Viscount removes the blindfold in order to display Ciel's eyes, the latter keeps them closed. After a moment, he opens them and calls for Sebastian. The lights go out, and the cries of many people are heard and the candles are suddenly relit to reveal Sebastian, who takes Ciel home as the police arrive at the scene.

Ciel and Sebastian continue to pursue Jack the Ripper and come to a confrontation at the house of the latest victim, Mary Kelly. They discover that the murderer is a combination of Madam Red and Grell Sutcliff, her seemingly bumbling butler, who is actually a Reaper. While Sebastian is busy fighting Grell, Madam Red attempts to kill Ciel, but she sees her sister's face in his and is unable to do so. Grell kills Madam Red because of this and her life is played back before his eyes, as Reapers can see a person's memories as they die. It is revealed that she loved Ciel's father, but he chose Rachel, her sister, over her. Eventually, she found someone she loved and married him, and was to have a child, but an accident killed her husband and caused the doctors to have to abort her baby and take out her womb to save her life, rendering her infertile. When one of her patients came to her and asked for an abortion, claiming children were a nuisance, something in her snapped and she followed the patient later that night and killed her. It was then that she met Grell, and the two of them murdered people as Jack the Ripper since then. Sebastian is ordered by Ciel to kill Grell.

Sebastian ends Jack the Ripper's reign of terror. Later, Ciel and Sebastian attend Madam Red's funeral and visit the grave of Jack the Ripper's last victim.

By the command of the Queen, Ciel is to secure Houndsworth, a village controlled by a nobleman Henry Barrymore. The supposed resort that the company was in for is, in fact, a dark and dreary place inhabited by a demon dog.

Ciel and his servants confront the real demon dog of the village of Houndsworth and end up taking it home.

Ciel assigns his servants to take a photo of Sebastian with a camera that reveals what is most precious to the subject that is not of this world (e.g., dead things). Sebastian evades their efforts over and over again effortlessly. In the end, Sebastian takes a photo of Ciel, who had fallen asleep at his desk, with Pluto behind him at the back window which leads to an amusing photograph that confuses the rest of the servants at the mansion. Sebastian later comments that it was an honor to learn that the thing Ciel most treasures that is not of this world is Sebastian himself. (Sebastian is a demon, therefore he is able to show up in the photo because he is not someone of the normal world). Later, Finny wonders how Sebastian can show up as he thinks that Sebastian is someone of this world.

Ciel and Sebastian visit a festival held on the frozen Thames River and enter an ice-sculpting contest for the prize, a ring with a slice of blue diamond called the Shard of Hope, which is important evidence in an investigation by Scotland Yard into the kidnappings of several young girls. Sebastian creates an ice model of Noah's Ark, complete with animals inside, but the Shard of Hope is apparently lost in the river following a bombing incident. Meanwhile, Elizabeth desperately looks for a present for Ciel's birthday. She later discovers the Shard of Hope in a toy ship she has bought.

Elizabeth becomes distraught and goes missing and Ciel and Sebastian head into the heart of London to search for her.

Ciel finds Elizabeth in a tower and rescues her after a brief battle against Drocell. Sebastian does not pursue a strange puppet that seems to have controlled Drocell as its master is far away. Later, Elizabeth celebrates Ciel's 13th birthday with a party at the Phantomhive Estate.

Ciel begrudgingly lets Prince Soma and his butler, Agni, who arrived from India in search of someone, take up temporary residence at the Phantomhive Estate.

Agni is revealed to be working for someone and Prince Soma plans to find out why. Along the way, a new goal is set to compete in the Curry Festival against Agni. At the end, Queen Victoria appears.

Queen Victoria attends the Curry Festival competition. Sebastian creates his curry with chocolate, Agni uses blue lobster, and another chef uses a mysterious spice that was given to him by Angela. Sebastian ends up winning with his curry bread, but the people who ate the curry with the mysterious spice become possessed and start attacking others. Sebastian and Agni fight them off and they are cured after a taste of Sebastian's curry bread. With the competition over, Prince Soma and Agni bid farewell to Ciel and Sebastian and return to their homeland.

Ciel is informed that the abandoned Ludlow Castle that his estate owns is haunted by ghosts and the workers are too spooked to continue remodeling it into a hotel, so he and Sebastian head to the castle to investigate. There they encounter the ghosts of two princes who were assassinated four centuries ago, Edward V and his brother, Richard. Ciel plays a game of chess against Edward V to pass the night, but he loses and Edward claims Sebastian as his winnings. Alone, Ciel solves the mystery behind the princes. The ghosts of Edward V and Richard thank Ciel and Sebastian before departing for the afterlife, and the remodeling of Ludlow Castle resumes.

Queen Victoria's butler informs Ciel that an abandoned monastery in rural Preston has been taken over by a cult that is possibly planning to overthrow the government, so Ciel and Sebastian head there to investigate with the Undertaker and Grell. They find that the cult uses a strange book known as the Doomsday Book to recruit new members and expose their pasts. Ciel is summoned one night and gets taken away by Angela, who reveals herself to be an angel.

Angela uses Cinematic Record to force Ciel recall his painful past, including the events surrounding his parents' murder, but Ciel eventually rejects her attempt to rewrite his past. She then attempts to purify the members of the cult, but Sebastian, Grell, and William incapacitate her. Angela destroys the monastery and escapes.

The body of John Stanley, a man who worked under the Queen, is found murdered in the River Thames. The Queen orders Ciel to retrieve an item from Stanley's body. Ciel goes to Lau, who controls the area where Stanley's body was discovered, for information. Lau does not recognize the name, but mentions a new drug, Lady Blanc, the name of which reminds Ciel of Angela. A large amount of the illicit drug is later found in one of Ciel's warehouses. Lau and Ciel are charged with drug trafficking, but Lau escapes. Ciel is separated from Sebastian, who is taken to the Tower. It is revealed that orders for the arrest were given by the Queen through her butler, Ash, with the drugs planted as a pretext.

Sebastian is tortured in the Tower of London by guardsmen and Angela. Ciel continues to pursue Stanley's case on his own, though Abberline declares his allegiance with Ciel. Ciel frees Sebastian by summoning him through their contract, and together they manage to get onto Lau's junk. Sebastian duels against Ranmao as Ciel confronts Lau, who turns his dao on Ciel. Abberline intercepts in time to take a fatal blow for Ciel and subsequently dies from the wound before Ciel's eyes. Sebastian strikes a blow at Lau to prevent him from continuing to fight, and escapes from the sinking junk with his master.

Ciel's servants show off their hidden talents in an effort to cheer up their master and protect the Phantomhive Estate. Within the mansion, Ciel teaches Elizabeth about chess until sundown. The backgrounds of Maylene, Bard, and Finian are revealed in a series of flashbacks.

Ciel and Sebastian head off to the Exposition Universelle in Paris to meet Queen Victoria and become wrapped up in the festivities of the Expo. A taxidermy monkey suddenly springs to life and destroys the lighting equipment, so Sebastian makes Ciel escape ahead to an elevator in the Eiffel Tower. Inside he finds Queen Victoria waiting for him. The two arrive at the top of the tower, where the Queen reveals that Ash granted her youth. Sebastian and Ash engage in a duel, raining debris down onto people below, so Ciel calls Sebastian off to prevent hurting them, which angers Sebastian. The next morning Ciel realizes that Sebastian has left him alone at the hotel and is non-responsive to his summoning, so Ciel attempts to make his way back to London on his own. He barely makes it to the port, where he spends the night sleeping cold and hungry on the docks. Meanwhile at the Phantomhive Estate, Ash takes control of Pluto and sets the property around the mansion on fire.

The Phantomhive mansion is burnt to the ground and Tanaka is seen writing in his diary alone in the debris. Ciel stows away in the cargo hold of a London-bound steamship, where he meets the Undertaker, who informs Ciel that he is about to die. The great fire in London has taken many lives yet it remains unabated, turning the once-beautiful city into Hell on Earth. Ciel wanders through the streets and eventually finds his servants trying to tranquilize a rampaging Pluto. He comes to a decision about his existence and gives the servants the order to kill Pluto. Ciel then makes his way to Windsor Castle, where he discovers Queen Victoria dead. The palace guards believe that Ciel murdered the Queen and shoot him. When the guards try to shoot him again, Sebastian appears and saves Ciel. The pair takes off toward the heart of London.

Ciel heads to the Tower Bridge that is still in mid-construction with Sebastian, where he finds the angel Ash. Ciel commands Sebastian to kill the angel. Ciel's servants have taken down Pluto, the Shinigami cut off the supply of souls that fuel Ash's strength, and Sebastian reverts to his true demonic form to defeat Ash. In the aftermath, a fake Queen Victoria emerges and urges London to begin rebuilding. Ciel wakes up being ferried by Sebastian on an ominous river to an unknown location. Sebastian hands Ciel Tanaka's diary, in which Tanaka details the former Lord Phantomhive's knowledge of his impending death. Sebastian and Ciel land at the rubble of a mansion, where Ciel calmly waits for Sebastian to take his soul. Ciel's final order to Sebastian is to make the process as painful as possible, so as to carve the pain of his life into his soul, to which Sebastian agrees. It is not known what happens to Ciel.