Cicely, Countess of Horbury

In the novel Death in the Clouds, Cicely, Countess of Horbury, Lady Horbury is the wife of Lord Horbury. She had travelled alone for a holiday to France which was largely spent gambling at Le Pinet. For the journey home, she boarded the Prometheus for its flight from Le Bourget to Croydon. Madame Giselle was found murdered enroute. When it was later discovered that Cicely owed Madame Giselle a large sum of money, she became one of the main suspects.

Lady Horbury is described as having a "carefully made-up Dresden china face", and she had blue eyes. She gives her address as Horbury Chase, Sussex, and 315 Grosvenor Square, London. She usually resides in the twin house in London, while Lord Horbury resides at Horbury Chase, as they do not get along.

Plot
On board the Prometheus, she meets The Hon. Venetia Kerr, who is a friend of hers. Poirot exchanges his seat with Miss Kerr, so that the two ladies can sit together.

During the flight, Lady Horbury breaks a fingernail, and asks the steward to summon her maid. She asks her maid to bring her red morocco case, from which she takes out a nail file.

When questioned by Inspector Japp, and later at the inquest, Lady Horbury says that she had never seen the deceased before. However, Poirot discovers that she had called on Madame Giselle the night before the flight to England, when he shows a reproduction of her to Georges, the concierge. Georges gives a slight start upon seeing the picture.

Poirot later asks Norman Gale to blackmail Lady Horbury, telling her that certain documents that formerly belonged to Madame Giselle have passed into his hands, and asking her for ten thousand pounds.

After Norman leaves, Poirot calls on Lady Horbury, and says that he will deal with the blackmailer if she will tell him the truth. She tells Poirot that she had first borrowed money from Madame Giselle eighteen months before the events of the novel, when she needed money because of her gambling habit. At that time, she and Raymond Barraclough had already become friends, and he told her that Madame Giselle lent money to Society women.

Lady Horbury says that Madame Giselle lent her only a small sum at first, and then as much as she wanted. However, Madame Giselle had gathered information about the places and dates of Lady Horbury and Raymond Barraclough's meetings, and she threatened to reveal this information to Lord Horbury if she was not repaid. Lady Horbury did not want her husband to find out about her friendship with Raymond, because it would give him a cause to divorce her.

Lady Horbury also tells Poirot that although the name she went by before her marriage was Cicely Bland, her real name is Martha Jebb, and she was born in Doncaster.

Agatha Christie's Poirot
In the the film adaptation of Death in the Clouds in Series 4 of ITV's Agatha Christie's Poirot drama series, the part of Cicely Horbury was played by Cathryn Harrison. Some of what happened to her is different from the original novel. Here she was in Paris with her husband to watch the Roland Garros tennis tournament. Also, unlike novel where Cicely met Venetia Kerr by chance on the plane, here Venetia is a friend of the family and Cicely's travelling companion. Lord Horbury leaves for home early because he is tired of her drinking and gambling. This left Cicely to watch the tennis finals with Venetia and then to fly home together on the Prometheus.

Agatha Christie's Great Detectives Poirot and Marple
In the NHK's anime adaptation Death in the Clouds, the character of Lady Horbury is voiced by Kotono Mitsuishi. Her backstory as the stage actress Martha Jebb, all skipped in the ITV adaptation, is narrated in detail exactly as in the original, most of this being given in an interview with Poirot. Like in the original, Poirot had engineered the event by asking Norman Gale to blackmail her. Poirot then steps in to offer to help, knowing that he would find her suitably receptive. Unlike the original, Poirot does not end up advising Cicely to divorce her husband. So this is a loose end in triangle between Lord Horbury and Venetia Kerr which is left unresolved.