In the novel Evil Under the Sun, Christine Redfern is the wife of Patrick Redfern, and a games' mistress. She stayed at the Jolly Roger Hotel with her husband, who eventually found the body of Arlena Marshall. In the hotel register, the Redferns' address is given as Crossgates, Seldon, Princes Risborough.
Christine is described as being an ash blonde, and she has very fair skin. She has a "fair serious face, pretty in a negative way, and small dainty hands and feet." According to her, her skin blisters and becomes freckled when she is exposed to the sun.
Poirot observes that Christine's face is neither a silly one nor a weak one, and that it has "plenty of resolution, courage and good sense".
Christine and her husband, Patrick, have an argument where she says that he wanted to go to the Jolly Roger Hotel, knowing that Arlena would be there. He tells her not to have such a suspicious attitude. This argument is overheard by Poirot.
As Patrick spends more time with Arlena, Christine spends more time sketching, even though she is a "most indifferent artist". Linda Marshall accompanies her on several sketching expeditions. On the morning of the murder, Christine wants to sketch at Gull Cove, and invites Linda to go with her.
After the murder is discovered, Poirot tells Colonel Weston and Inspector Colgate that Christine may have had "ample cause" to commit the murder, and that it was possible for her to commit a murder, but not to kill someone by strangulation. He says that for all her unhappiness and jealousy, she is not a woman of strong passions. He suggests that if she wanted to commit a murder, she would use a different method, such as arsenic in a teacup. He also says that she is physically incapable of committing the crime, as her hands and feet are smaller than average.
Linda Marshall says that Christine may have wished that Arlena was dead, but she could not have killed anyone, as she is not violent. Patrick later says the same thing, that there is no violence in Christine.
Christine later tells Poirot, Colonel Weston and Inspector Colgate that she had overheard a conversation between Arlena and someone who was blackmailing her.
While searching the rooms of the hotel guests, Poirot notices the "traces of two different individualities" in the Redferns' room. There is a neatness which Poirot associates with Christine, and a "picturesque disorder" which he associates with Patrick.
Towards the end of the novel, the Redferns join Poirot and other hotel guests on a picnic. Poirot observes Christine springing lightly from stone to stone, and sees that Patrick is always near her. Christine is also able to run lightly across a narrow plank bridge across a river.
On returning from the picnic, Gladys Narracott tells Christine that she is worried about Linda, as she could not wake her up. Christine and Poirot go to Linda's room to see. It is discovered that Linda took Christine's sleeping tablets, and overdosed on them.
Poirot later reveals that Christine had been playing a part since her arrival at the hotel, that of the "poor little wife". She had spoken of her tendency to blister in the sun and her fear of heights, emphasizing her frailty and delicacy. She had also mentioned being a former schoolteacher, which emphasized book learning and a lack of athletic ability. However, Poirot reveals that Christine had been a games mistress at a school, and she was athletic.
Poirot reveals that the conversation between Christine and Patrick which he had overheard, in which Patrick told her not to be jealous and suspicious, was staged.
It is revealed that Christine went to Linda's room on the day of the murder, while Linda was out. She altered Linda's watch, adjusting the time forward by twenty minutes.
Christine applied artificial suntan before going to Gull Cove with Linda. After leaving Gull Cove, she went to Pixy Cove and lay down on the beach. When Patrick and Miss Brewster discovered the body, it was actually Christine, and not Arlena. After Miss Brewster had left to notify the police, Christine returned to the hotel. She took a bath to wash off the artificial suntan, and then went to the tennis court.
Poirot reveals that Christine had been involved in the case of Alice Corrigan. Under the name Christine Deverill, she found the body and reported it to the police. The time of day that she claimed to have found the body gave the dead woman's husband Edward Corrigan an alibi. The Surrey police are able to identify Christine from a photograph.
Poirot also reveals that he had organised the picnic to test whether Christine was truly afraid of heights, as she had claimed. When she was able to run across the narrow plank bridge without suffering giddiness, he knew that she had been lying about her fear of heights. Since she had told one unnecessary lie, he considered it possible that other things she had said were lies as well.
In the 1982 TV adaptation of Evil Under the Sun, starring Peter Ustinov as Poirot, Christine was portrayed by Jane Birkin, who also played Louise Bourget in an adaptation of the novel Death on the Nile.