Alfred was "quite a good-looking man with a thin dark face and eyes set rather too close together". He was known in the privacy of the family as Flash Alf, as he was the black sheep of the family. He had not actually been to prison, but had been near it, and had been involved in some dubious deals in the past. His father said that he had always been a coward and a liar.
Alfred was in the Ministry of Supply during the war, but left it abruptly under questionable circumstances. At the time of the novel, Alfred had said he was in insurance.
When Inspector Craddock met Alfred, he found his face vaguely familiar. This was because Alfred had been involved in a deal involving tinned food with a man called Dicky Rogers, who was known to the police. Alfred had always been on the outskirts of the racket, with an innocent reason for being involved, and nothing could be proved, but the police were sure that he made a small, steady profit.
Alfred does not provide an alibi for the day of the murder, saying he cannot remember what he was doing. However, Sergeant Leakie saw him at the Load of Bricks, a lorry pull-up on the Waddington-Brackhampton Road. Alfred had been with Chick Evans, who was known to be one of the Dicky Rogers gang. Alfred had boarded a bus in the direction of Brackhampton a few minutes later.
William Baker, a ticket collector at Brackhampton station, had clipped the ticket of "one of Miss Crackenthorpe's brothers" on the night of the murder, just before the departure of the eleven-fifty-five train for Paddington. It was not confirmed which brother it was, but the police believed it was Alfred.
Alfred had told Lucy Eyelesbarrow that he had fallen for her, and had asked her to marry him. Lucy felt that there was a quality of charm about him, perhaps due to sheer animal magnetism.
Alfred was taken ill, along with the rest of the Crackenthorpe family, after eating a curry. Dr Quimper was called to attend them, and found evidence of arsenic in the curry. Dr Quimper was of the opinion that no one had had enough to cause death. However, Alfred appeared to have a serious relapse, and died. It was believed that he had been given a second dose of arsenic.
In BBC's 1987 adaptation of 4.50 from Paddington, the part of Alfred is played by Robert East. In this adaptation he is not killed but is suffering from a terminal illness which he says Dr Quimper failed to diagnose so that by the time it was finally discovered, it was too late. Miss Marple later surmised that it was possible that Quimper might have deliberately refrained from diagnosing the illness.
In NHK's anime adaptation 4:50 from Paddington, Alfred is killed in the same manner as described in the original novel. Here his occupation is described as an insurer. The police know that he needs money but there is no mention of his shady activities. The voice actor behind the character is not credited.