Horbury is described as being a "dark man with a smooth face". He is quite competent at his job, but has a way of creeping about silently, which some members of the household do not like. He is described as creeping about the house "like a cat".
When Tressilian tells Horbury that Superintendent Sugden came to the house, Horbury accidentally drops a coffee cup, breaking it. He asks what the Superintendent wants, and is relieved when Tressilian says that he is collecting for the Police Orphanage. Horbury then leaves the house to go to the cinema, as it is his night off.
Horbury meets Doris Buckle at the cinema, where they watch Love in Old Seville. He sees her home after the picture, and then returns to Gorston Hall. This gies him an alibi for the time of the murder, as Doris says that he was with her in the cinema the whole time. In addition, Tressilian states that there was no way Horbury could have returned to the house without being seen, as the doors were locked and bolted, and he would have had to pass through the kitchen if he came in through the back door.
At first, Horbury claims that he did not know the stones Mr Lee kept in his safe were diamonds, and that he did not know they had been stolen. However, he later says that Mr Lee had talked to Alfred after discovering the theft of the diamonds. Poirot catches him in this lie, and Horbury admits that he had overheard Mr Lee telephoning to someone about it.
It is later revealed that Horbury has a reason to e scared of the police, as he had been accoused of extorting money under threats, and modified blackmail. The case could not be proved, so he was let go.
In the 1995 ITV adaptation of Hercule Poirot's Christmas, Horbury is portrayed by Ayub Khan-Din. The characterisation is fairly similar to that in the book. Police inquiries also revealed that he has reason to be fearful of the police (he dropped a coffee cup when Tressilian mentioned that Superintendent Sugden was coming to Gorston Hall). According to Sergeant Coombes, Horbury was charged with "extorting money under threat" while working for someone else in Bedfordshire. However Horbury had an alibi for the time of Simeon Lee's death--he had been at the cinema with his girlfriend.