Arthur is an unknown writer and a relatively inexperienced eye doctor who had served aboard a ship for some time.
In 1889, he receives a letter invitation to the Phantomhive manor, at a party with numerous people of renown stature. The earl appears to be fond of one of Mr Wordsmith's published writings in a relatively obscure magazine, that being the sole reason for his invitation.
Arthur's character is based on the famous writer Arthur Conan Doyle, who gave life to the now most famous detective Sherlock Holmes. He has a steadfast sense of justice and a cool, analytical mind. He has a habit of jotting down notes in the cuffs of his clothing for reference in his novels.
At night, one of the guests, Lord Siemens is being found dead in his room and this starts the Phantomhive Manor Murders. Due to the rain, nobody can leave the manor and they have to cope with the situation as others of them are being murdered (that including the butler, Sebastian).In this case, Arthur will play the role of the detective, desperately trying to find the culprit, even if at first it seems impossible.
Later after Siemens death and before he was found murdered, Sebastian tells him that "he leaves the young master in his hands", this somehow making Arthur feel that something was not right in that manor.
At the end of the arc, just after his carriage leaves the mansion, he realizes Mr. Jeremy's true identity as Sebastian and heads back for confirmation. Sebastian and Ciel reveal the true unfolding of events and that they had framed Woodley for Earl Gray's murder. Sebastian also reveals himself as a demon in order to give Arthur the incentive and inspiration to continue his writings.