The Butler, Solving (その執事、解決, Sono Shitsuji, Kaitō) is Chapter 48 of the Kuroshitsuji manga.
Arthur states that he cannot believe that "something so unreal" could be happening. Sebastian is surprised, saying that, if Arthur had just gone back, he would have returned to his "peaceful reality". Sebastian then asks why he came back, even though Arthur was trembling. Arthur replies that, if his "uncomfortable feeling " wasn't just a feeling, then he would have to go after the Yard's carriage immediately. Ciel laughs at this, saying that Arthur's sense of justice is strong, and asks if Arthur realizes that, if he knew the truth, he wouldn't be able to return home. Arthur is shocked at this, but Ciel passes it off as a joke. Ciel then tells Arthur that it was as he guessed ‒ Woodley hadn't committed the murders, but deserved to be in the Yard's carriage. Arthur is confused at this, while Ciel tells Sebastian to go and prepare some elevenses. Arthur is hesitant to go with them, but Sebastian jokingly tells Arthur that they won't eat him.
After the refreshments have been served, Ciel asks Arthur how he knew that Sebastian was alive. Arthur replies that he had no conviction that Sebastian was alive, but rather, a vague sense of discomfort, as he felt that Sebastian and Jeremy were just "so perfect," that "it was strange instead", and that the moment he heard Jeremy's parting words, he realized he was feeling discomfort because of "the possibility of something unreal"—that Sebastian was still alive. Arthur says that after that, he was unable to contain himself and returned to the mansion. Arthur also remarks that he felt it was strange that, at the time of Siemens' murder, he did nothing, even though before, he had always acted so swiftly. He also felt strange when Ciel was suspected and Sebastian did not say a word in his defense, even though Ciel is Sebastian's master. Arthur asks if the reason that Sebastian said nothing was because he knew that the suspicion on Ciel would be lifted once the next murder occurred ‒ his own.
Sebastian says that, while he did realize the next murder would clear all suspicion from Ciel, that was not why he did not come to Ciel's defense—rather, he did not do so because he was taken aback by Ciel predicting something would be set up, but quickly giving in and going to sleep, leaving Sebastian to deal with the mess. Ciel, however, thinks Sebastian did not defend him because he thought Ciel deserved it. After Arthur expresses his shock, Sebastian says that both he and Ciel knew that there was " a person mixed up in the dinner party that wanted to torment the young master". Sebastian also reveals that they suspected that Siemens would "probably be made a sacrifice for it," and that Sebastian would be killed.
Two days earlier, Sebastian and Mey-Rin found Georg von Siemens' body. At the time, Sebastian heard something crack after Siemens screamed. Sebastian is shown to look around the room while everyone else is focused on Siemens' body, but, seeing nothing broken or smelling any blood, he concludes that there would probably be some sort of bottle that had contained poison in the hearth. Arthur asks why Sebastian did not immediately say anything about it, as it would have prevented Ciel from being suspected, to which Sebastian replies that Ciel had chosen to simply observe, so he did the same. Ciel adds that he first thought that Siemens' murder had been a set-up and that he also guessed that Siemens had taken the poison willingly.
Sebastian then reveals that, when Ciel sent him to collect the ashes, the true meaning of the order was to "inspect the hearth carefully." Sebastian remarks that Ciel is a cruel master since he had given him that order despite knowing that Sebastian would be killed if he went through with it. Ciel replies that he did not think that everything would go as they expected for so long. When Arthur expresses confusion over this statement, the scene cuts back to the night when Sebastian was killed, with Sebastian explaining his death was a scenario not decided by a God or fate, but rather his master, the timing also having been decided by his master, and the deed committed by the criminal his master had expected. Sebastian is shown to have discovered glass shards in the hearth, but instead of the shards forming one bottle, they form two. Sebastian then reveals that the "one who came to torment [his] master" and the one who murdered him was Charles Grey.