The Butler, Setting Sail (その執事、出港, Sono Shitsuji, Shukkō) is Chapter 51 of the Kuroshitsuji manga.
Charles Grey stabs Karl Woodley in the head before complaining to Charles Phipps and John Brown that he could not manage to harm Ciel. Phipps reprimands Grey and remarks that it is because he does not think about the consequences of his actions before he does things. Grey then changes the subject, saying he wonders what the Queen is doing, to which Phipps replies that mere butlers such as themselves do not need to know, as long as they do everything according to the Queen's wishes.
Inside the Phantomhive household, Sebastian talks to Mey-Rin, Finnian, Baldroy, and Tanaka about their chores, then introducing them to Snake, who has become the household's new footman. Snake enters the room with his many snakes, causing all of the other servants except for Sebastian to run away. Sebastian remarks that there is nothing to be afraid of, as the snakes will not attack or kill anyone unless Snake orders them to.
Sebastian smacks Snake's back and orders him to introduce himself, to which he shyly obeys. Finnian becomes confused with how Snake ends every sentence with "says Oscar", "says Bronte", etc., until Oscar, one of the snakes, explains that Snake is Snake's name. Snake and Oscar then begin introducing the other snakes until Sebastian interrupts them, telling them to do it at another time since they have work to do, then adding that Snake will be the household's new footman.
The servants start preparing food in the kitchen, and Baldroy questions Sebastian as to whether he is actually serious about hiring someone as suspicious as Snake. Sebastian replies that it does not matter whether he is suspicious or not since Ciel had asked him to hire him, and also because Baldroy and the other servants could be considered "suspicious" as well. Sebastian then goes on to say that he does not care who Snake is, but, if he ever tries to harm Ciel, Sebastian will kill him.
Sebastian then brings food to Ciel, who is having tea and reading the newspaper. Ciel asks how well Snake does his job, and Sebastian replies it will take some time to train him, but he is a fast learner so it should be alright. They have a conversation about how Sebastian is good at teaching people things, but then he teases Ciel saying he might not be as good a teacher as he had thought since Ciel had not learned much from their dancing lessons.
Ciel gets annoyed and goes back to reading his newspaper, then seeing that the front headlines talk about a hospital that can bring people back to life. Sebastian notices that Ciel is bothered by something and questions what is wrong, to which Ciel replies that it is nothing important. Lau and Ran-Mao then suddenly come through the door, with Lau asking how Ciel is and claiming that he was there to steal Ciel's breakfast, although Ciel had already finished. Ciel tries to questions Lau further, but Lau then sees Sebastian and questions why he is not dead. Ciel interrupts and tells Lau to listen when people are talking. He then asks why Lau was actually there since he could not possibly be there just to get a free breakfast.
A conversation about a hospital that revives the dead starts between Ciel, Sebastian, and Lau. Ciel says he has little interest in the occult, but Lau then remarks that it may not be the occult and that Karnstein Hospital has been doing a lot of shopping at the back docks that Ciel has Lau in charge of. Ciel questions if they are selling or buying drugs, but Lau replies that it is not drugs, but people. Lau then remarks that the hospital has apparently been buying foreign slaves illegally for a while, but lately, the numbers are quite unusual, and he doubts that the hospital could even fit that many people. Lau remarks that it seems like a bad thing for a hospital like that to be featured in regular society's news, to which Sebastian asks if he means that the "revival of the dead" article in the paper may be caused by the hospital performing illegal human experimentation. Lau tells him that that is right. Ciel says that if that is true, then it is an interference in the regular society by an underground power, but says that it may be fixed easily if they can do it quick enough, so he orders Sebastian to investigate immediately. Sebastian then tells Ciel to leave it to him.
Later, Ciel looks out one of his windows, towards Finnian and Snake pointing to an arriving horse carriage, while he remarks that reviving the dead sounds like a foolish thing to believe. He then notices the carriage, which contains Elizabeth, who comes bursting through his doors to greet and hug him. She excitedly tells him that they are having a family trip on a luxury cruise ship for three weeks from the 17th of April. Ciel is less than enthused, telling her that it is impossible since he has work to do. Elizabeth nags that the ship is supposed to be the most luxurious ship in the world, and that her mother said it would be good if Ciel could take a rest from work every once in a while. Ciel says that he appreciates the offer, but he cannot take that much time off from work. Elizabeth becomes sad, so Ciel says that he can go on a trip for a few days if it is somewhere close. Elizabeth says that anywhere is fine and hugs Ciel.
Elizabeth soon leaves, and Sebastian appears out of nowhere in front of Ciel, asking Ciel what he is grinning at. Ciel screams and tells Sebastian not to surprise him like that, adding that he was not grinning. Ciel then questions what is with his outfit, which is a doctor's attire. Sebastian says that he dressed that way in order to get information easily. He says that what he found out is that Karnstein Hospital's upper-rank doctors, including the director, Rian Stoker, have opened an association called the "Aurora Society". The Aurora Society is a secret society made up of doctors who have "The complete salvation of mankind through medicine" as their motto, and the members of the society conduct illegal human experiments daily within the hospital. The Aurora Society also apparently holds presentations for the results of their experiments regularly, collecting donations from nobles. Sebastian says that, even with all of this information, there was no sign of the slaves, the actual human experiments, or signs of reviving the dead inside the hospital. Ciel remarks that all of this seems very fishy and Sebastian agrees, saying that there is definitely a clue to be found within the Aurora Society. Ciel asks where the Aurora Society's next meeting is, to which Sebastian replies that it is to be on a ship that departs from Southampton Port on the 17th of April. Ciel begins saying that meeting on a ship seems like something nobles would do, but then remembers about Elizabeth inviting him to a ship for the same day. Ciel hurriedly asks what the name of the ship is, to which Sebastian replies that it is the Blue Star Line's luxury ship, Campania.
Ciel, Sebastian, and Snake are then boarding a ship, with Snake's snakes also boarded in a crate. The other servants remark that it is cool that Snake gets to go as well, to which Sebastian replies that it is because a footman's job is to accompany his master on outings. He then tells the servants to do their jobs properly while they are gone, to which they say they will comply. Sebastian then says goodbye and the three board the ship. After they get on, a man asks Mey-Rin if she knows where the second class entrance is, and she says it is probably in the east direction. The man then thanks her and says he will treat her to some tea later, asking for her room number. Mey-Rin becomes flustered and exclaims that she is only there to see someone off. One of the ship's employees remarks that the bridge will be pulled up soon, to which the man hurriedly says to Mey-Rin that he will invite her for tea again if he makes it back in one piece. Baldroy says that the man seemed like a playboy, and Finnian remarked that he had big glasses. The man is then shown running quickly towards the ship, saying he would be killed if he missed it.
Ciel, Sebastian, and Snake make it to the top floor of the ship, with the other servants on the ground, waving at them while seeing them off. The man who had been talking to Mey-Rin is seen onboard, saying he made it just in time. The man then takes off his hat and reveals that he is Ronald Knox.