Buck
Buck was a British child laborer in London around the mid-nineteenth century.
He and his brother Dooley worked in a Whitechapel factory in 1868, where Buck ended up being attacked by Tom Coulton one of the adult laborers of the factory, for not working hard enough. Dooley intervened, after which Coulton attacked him instead, allowing Buck to run off and find help.
When he returned, Dooley's hands were covered in blood, and there was a dead body lying on the ground. Dooley was briefly suspected of the murder of John Wilkins, but his name was soon cleared when Jacob and Evie Frye identified Coulton as the murderer.
Buck and Dooley encountered the Frye twins again later that year, when they were investigating the disappearance of Arthur Conan Doyle. The two boys had no information about Doyle's location, but did point out ways for the Assassins to discover new leads.