Dr Gérard is tall and middle-aged. He and Sarah King first met in Cairo, when he helped to carry one of her suitcases when no porter was available. At the beginning of the novel, they meet again in the Solomon Hotel, in Jerusalem.
In the lounge at the Solomon Hotel, Sarah and Dr Gérard observe the Boynton family. He notices that Sarah's interest in them is motivated by her interest in Raymond Boynton. After Sarah leaves, he continues to observe the Boyntons, as he senses that there is something there of psychological interest. He notices that underneath the harmless family talk, there is an undercurrent of hatred.
Dr Gérard later encounters Ginevra Boynton, who tells him that she is really the heiress to a throne, and has enemies all around. She asks him to help her get away.
Dr Gérard travels to Petra, together with Sarah King, Lady Westholme, and Miss Pierce. He argues with Lady Westholme about the League of Nations, as she is an ardent supporter of it, while he prefers to "be witty at the League's expense".
Dr Gérard has "a good head for heights", but he is kind and reassuring with Miss Pierce, who is afraid of heights. He climbs behind her, holding a stick between her and the sheer drop, which helps her to overcome the feeling of vertigo.
On the day of the murder, Dr Gérard goes for a walk with Sarah, Jefferson Cope, and some members of the Boynton family. He returns to the camp early, as he is suffering from an attack of malaria, which he says is a legacy from a visit to the Congo.
Colonel Carbury later asks Dr Gérard to tell Poirot facts about the case. Dr Gérard tells them that when he returned to his tent on the day of the murder, he could not find his case of drugs at first, as someone had moved it from where he had originally placed it. He had intended to treat himself with an intravenous injection of quinine, but was unable to find his hypodermic syringe. He took a large dose of quinine by mouth instead. On getting up the following morning, he found the hypodermic syringe behind a case of bottles on his dressing table, and was positive that it had not been there before.
Dr Gérard also tells Poirot that there was a mark on the victim's wrist, such as would be made by the insertion of a hypodermic syringe. Dr Gérard had also examined his case of drugs, and found that his stock of digitoxin was diminished.
Dr Gérard expresses the opinion that the evidence in the case is bound to be inconclusive, and they may know that murder has been done, but it will be difficult to prove. Poirot asks if he is satisfied that the case should rest that way, and he says that he is not. Dr Gérard explains that it is his instinct to preserve life, not to hasten death, and so even though his conscious mind believes that Mrs Boynton's death was a good thing, his unconscious mind rebels against it.
Dr Gérard tells Poirot and Colonel Carbury that Ginevra Boynton is in a dangerous condition mentally, as she has begun to display symptoms of schizophrenia, with advanced delusions of persecution. He explains that this is dangerous because it is the beginning of what is often homicidal mania. He considers it possible that Ginevra might have killed her mother, but he is almost certain that she would have chosen a more spectacular method.
Dr Gérard later tells Poirot that he is going to attempt to treat Ginevra. He arranges with Lennox and Nadine Boynton for Ginevra to go to Paris and enter one of his clinics, and after her treatment, she will have her training for the stage.
At the end of the novel, Ginevra performs in a production of Hamlet, implying that Dr Gérard's treatment has been successful. It is also implied that Dr Gérard and Ginevra are in a romantic relationship, as she addresses him by his first name, and he calls her "chérie".
Appointment with Death (1988 film)
This character is not featured in the 1988 film adaption of Appointment with Death.
Appointment with Death (2008 ITV adaptation)
In the 2008 ITV adaption of Appointment with Death, Theodore Gerard is portrayed by John Hannah. Here his backstory and role in the plot is changed considerably. Like in the original, he is a psychiatrist (he introduces himself to Poirot as a "bonce doctor") but he is British and not French. He travels with the Boyntons and Poirot to the archaeological dig at Ain Musa. He is chatty with Poirot during the journey and seems knowledgeable about the Boyntons, supplying Poirot with all sorts of background information.
It is only during the denouement that Poirot exposes Gerard for who he really is and the role he played in the events. Many years before Gerard had been a houseguest at the home of Lady Boynton who was at that time Mrs Pierce. Gerard had an affair with Celia Westholme, at that time a housemaid of Mrs Pierce and had got her pregant. Celia Westholme later gave birth to Jinny who was handed over and adopted by Mrs Pierce.
Years later, Celia Westholme had built up a new identity as a famous traveller and writer and had become Dame Celia Westholme. She discovered that Mrs Pierce, now Lady Boynton, had been badly mistreating her adopted children, including Jinny. They had been beaten and tortured in various ways. Dame Celia sought out Gerard in Vienna (presumably he was there to train in psychiatry). She persuaded him to join in a scheme to exact revenge and punish Lady Boynton for what she had done to Jinny, their daughter. See here (click expand) for details on how they made killed Lady Boynton after making her suffer.
Poirot revealed during the denouement that he remembered when Gerard testified at a case in Edinburgh which he was involved in. At that time, Gerard was a psychiatrist but the clerk of the court read out his qualifications and this showed that he was originally an anaesthetist. According to Poirot, Gerard played a key role in executing various points of misdirection in the murder, in many cases using his expertise as an anaesthetist:
- He gave Dame Celia a syringe with a small amount of a morphine concoction, enough to paralyse Lady Boynton so that she would be roasted to death in the sun unable to call for help.
- He drugged himself to fake the symptoms of malaria so that he would be brought back into the camp from the excursion to continue with the other parts of the plot. This was done skilfully enough to fool Dr Sarah King.
- Back in camp, he asked Jinny to stay with him in his tent and then drugged her to give himself an alibi.
- He planted among Lady Boynton's clothes a ball of wax encasing the blood of a goat. This later melted, spilling blood all over, misleading observers as to the time and cause of death.
- Later, he drugged Nanny Taylor with mescaline which made her susceptible to suggestion. He then burdened her mind with guilt for being the one who took orders from Lady Boynton to beat the children. This caused Nanny Taylor later to commit suicide.
After the denouement, knowing that Poirot had seen through the entire plot, Gerard injected digitalis into Celia Westholme and himself, killing both of them before they could be arrested.