Geoffrey Roberts

In the novel Cards on the Table, Dr Geoffrey Roberts is a successful physician, who is bright but showing signs of age. He is described as a "cheerful, highly-coloured individual of middle age", with small "twinkling eyes, a touch of baldness, a tendency to embonpoint and a general air of well-scrubbed and disinfected medical practitioner". His manner is cheerful and confident. When playing bridge, he tends to overcall his hand, but he says that he has found that it usually pays off.

Dr Roberts lives at 200 Gloucester Terrace, W.2. His telephone number is Bayswater 23896.

Mr Shaitana had met Poirot at an art exhibition and wanted Poirot to come to dinner to view his unique collection--a group of people he believed to be murderers who had gotten away with their crimes. Dr Robberts was one of the guests and part of Shaitana's "collection". Although Shaitana did not specify the kind of crime he believed Dr Roberts to be involved in, over dinner he alluded to doctors having opportunities to poison people. Dr Roberts jokingly replied that when doctors poison their patients, it is entirely by accident.

Dr Roberts knew Mr Shaitana slightly, and found him amusing, because he was "such a fantastic fellow". He also knew Mrs Lorrimer slightly, as he had met her playing bridge before.

Dr Roberts is from Shropshire, and was born in Ludlow. His father was also a doctor, and had a practice there. When he was fifteen years old, his father died. He was educated at Shrewsbury, and went in for medicine, like his father before him. He is an only child, and is unmarried.

Dr Roberts came into partnership with Dr Emery, who retired about fifteen years before the events of the novel.

Dr Roberts' secretary, Miss Burgess, mentions a former patient of his, Mrs Graves. She had developed fancies that he was trying to poison her, and so he had been happy to let her go to another doctor. Another of his former patients was Mrs Craddock.

Mrs Craddock was always sending for Dr Roberts. On one occasion, she and Mr Craddock were having a row, and Dr Roberts arrived in the middle of it. Mr Craddock shouted at Dr Roberts, accusing him of unprofessional conduct, and threatening to get him struck off the Medical Register. Dr Roberts told Mr Craddock that his wife was hysterical, and that if he thought it over, he would see that the whole thing arose from her disordered imagination. Dr Roberts then washed his hands in the dressing room, before going on to his next case. Shortly after that, Mr Craddock contracted anthrax, and died.

After the death of her husband, Mrs Craddock planned to travel to Egypt.In preparation for her trip, she went to Dr Roberts for inoculations against typhoid fever. She later died of blood poisoning while in Egypt.

Superintendent Battle thought that Dr Roberts had killed Mr Craddock by infecting his shaving brush, and might have killed Mrs Craddock by introducing bacteria into her bloodstream when she came for her typhoid inoculations.

Towards the end of the novel, Dr Roberts receives a letter from Mrs Lorrimer, in which she confesses to killing Mr Shaitana, and says that she is taking a short cut out. He rushes to her house, and finds her dead in her bedroom. He tries artificial respiration, but it is too late.

Poirot later reveals that Dr Roberts killed Mr Shaitana, and later killed Mrs Lorrimer. He had seen that she was terminally ill, and decided to make her a scapegoat. He forged three letters in her handwriting, to be sent to himself, Anne Meredith, and Major Despard. He then went to Mrs Lorrimer's house, found her asleep under the influence of the sleeping draught she had taken the night before, and injected her with a drug, causing her death. Dr Roberts at first says that he injected Mrs Lorrimer with a restorative, as a last effort to bring her round. However, Poirot reveals that the drug Evipan was found in Mrs Lorrimer's body. When Superintendent Battle mentions that they may bring a further charge for the murder of Charles Craddock and possibly his wife, Dr Roberts gives up, saying that he is throwing in his hand.

Poirot explains that when examining the bridge scores, he noticed that there was a grand slam in the third rubber. He found out that Dr Roberts was dummy during that hand, and that he had bid the grand slam in his partner's suit, so that she played the hand. This gave him the opportunity to kill Mr Shaitana, and also ensured that none of the other players would look up and see him doing it, as they would all be concentrating on the game.

Poirot also explains that by asking all the suspects to describe what they remembered of the room in which Mr Shaitana was killed, he found that Dr Roberts was the most likely person to have noticed the dagger, as he was a natural observer of all kinds of trifles. However, he remembered practically nothing of the bridge hands, which suggested to Poirot that he had had something else on his mind the entire evening.

Superintendent Battle had earlier said that the other killings attributed to Dr Roberts, those of Mr and Mrs Craddock, did not bear similarities to the murder of Mr Shaitana, as medical methods had been used to kills both the Craddocks. However, Poirot explains that when examined from a psychological point of view, all three murders were almost exactly the same. They were all what he called public murders. He says that in each time, Dr Roberts reacted the same way. When pushed into a corner, he seized a chance and acted at once, showing "sheer bold audacious bluff", just like his bridge playing.

Portrayals
In the film adaptation of Cards on the Table in Series 10 of ITV's Agatha Christie's Poirot drama series, Dr Roberts has a different first name "John". His backstory and therefore his motive for the murder of Shaitana is somewhat altered. Here, he has a homosexual relationship with Charles Craddock who is also his bridge partner. Craddock's wife Dorothy found out about it and had an angry argument with Roberts. Roberts knew that at some point Mrs Craddock would expose him. As Mrs Craddock was preparing to go on a trip to Egypt and needed inoculations, Roberts inoculated her with an infected needle. She developed blood poisoning in Egypt and died there. Poirot surmised that she must have met Shaitana there and talked to him about her suspicions. Dr John Roberts is portrayed by Alex Jennings.

In Cartes sur table, the French adaptation for the series Les Petits Meurtres d'Agatha Christie, the parallel character is Emile Barillon.