The Butler, Under Lock and Key (その執事、優勝, Sono Shitsuji, Yushō) is Chapter 81 of the Kuroshitsuji manga.
In precedence to the boat parade, Sebastian Michaelis hands over an appropriately sized suit for Ciel Phantomhive, having had it specially tailored by Nina Hopkins. Those in Blue House that participated in the cricket tournament has their picture taken. Lawrence Bluewer then briefly explains the parade sequence: they are to go along River Thames, and upon approaching the Windsor Castle, they are to take off their hats and salute Queen Victoria; afterward, they will throw the flowers from their hats into the river and return.
Once the sun has set, Herman Greenhill orders Edward Midford to light St. George's fire and lanterns are released. Blue House rows to Queen Victoria, John Brown, Charles Grey, and Charles Phipps. They salute her, and Ciel inwardly promises to present to her the truth behind Derrick Arden. Lawrence then points out that they have not expected to win, so they have not practiced for the parade even once. Following that unfortunate disclosure, they lose their balance on the boat and fall into the river; the flowers from their hat scatter widely. The audience is amused. Fireworks go off, and Lawrence comments on its beauty.
Afterward, the celebration begins, and people dance and enjoy the feast. Cheslock, along with the other musicians, perform for their entertainment. At the end of the festival, Ciel returns to the Sapphire Owl dormitory, and discovers his invitation to the midnight tea party on his bed; his invitation includes a special flower that one must wear to mark his right to attend the party.
At midnight, Clayton comes to pick up Ciel, who has donned on the flower. P4 greets Ciel, and Cheslock plays sinister music on the pipe organ. P4 leads the way to a covert door, that upon opening, reveals the garden where Johann Agares and the headmaster are at. Johann welcomes the prefects, their Fags, and Ciel, and tells them to sit on the designated table with the headmaster. Before they can toast and honor the occasion, however, Ciel states that he must, first, meet Derrick Arden and his friends (i.e. Richard Greenson, Hans Hardy, Robert Isaac, and Ewan Thewlis). He says that he was asked by their respective parents to persuade them to come home. He adds that he could not do as requested because he was met with the most bizarre circumstances: their sudden transfer from Red House to Purple House, and the day of the fire where they were not present during the evacuation even though Gregory Violet has claimed that they are "all safe." Ciel says that five people disappearing from a strictly supervised public school is a very strange incident, and suggests to the headmaster that he calls Scotland Yard.
Johann disagrees, stating that they are all here, and directs their attention to another door. Derrick Arden, then, enters through it, remarking that the place smells like tea, and Ciel is shocked.