Lady Westholme

Lady Celia Westholme, also known as Dame Westholme in Agatha Christie's Poirot, is the main antagonist of Agatha Christie's Appointment With Death featuring Hercule Poirot. She is the murderer of the tyrannical Lady Boynton, committing the murder in order to keep her true identity as a former criminal secret.

She was portrayed by the late Lauren Bacall in the novel's 1988 film adaptation, and later by Elizabeth McGovern in Agatha Christie's Poirot, of which it adapted the book in 2008.

Overview
In the original novel, Lady Westholme is a former criminal once imprisoned in the very same prison where Lady Boynton, the book's victim, served as its former prison warden. She later became Lady Boynton's secretary and attempted to reach for higher social status, but was threatened by Lady Boynton, who attempted to leek her secret identity if she did not submit to her. The threat made by Lady Boynton, detailing how she would never forget anything, was originally thought to be a threat to Sarah King, but it was revealed to be a threat to Lady Westholme instead.

Without any choice, Lady Westholme killed Lady Boynton to keep her social status unharmed. Disguised as an Arab servant, she had committed the murder via poisoning the victim with a syrince filled digitoxin, and then relied upon the suggestibility of Miss Pierce to lay two pieces of misdirection that had concealed her role in the murder.

During Poirot's relvelation of the truth, Lady Westholme eavesdropped all of it in an adjoining room. Realizing that her criminal history is about to be revealed to the world, Lady Westholme commited suicide.

In Agatha Christie's Poirot
In Agatha Christie's Poirot, however, the characterization of Lady Westholme comes much more sympathetic and caring than that of her novel counterpart. In the adaptation, she was renamed as Dame Celia Westholme, who was a professional writer. She served as a maid in the home of Lady Boynton (who was then Mrs. Pierce) before.

When she was younger, she had an affair with Dr. Gerard and gave birth to Jinny Boynton (an original character not seen in the novel), and was sent away to a nunnery in Ireland while Lady Boynton kept the baby. However, when Dame Celia and Dr. Gerard found out that Lady Boynton had abused all of the children that were in her care (including Jinny) even for a short while (like Mr. Cope), they decided to kill her in order to stop her abuse.

Before the murder occured, Westholme managed to paralyze Lady Boynton through the poison injection, before she and Dr. Gerard (who managed to infect himself with malaria for alibi) faked her apparent death under the exposed sun. When people discovered Lady Boynton's situation, Dame Westholme went up to Lady Boyton's bench and stabbed her in the abdomen, where Dr. Gerard placed a piece of wax covered with goat's blood, with it melt under the sun's scorch, seeping blood upon the victiom's body and pretending to be the victim's blood.

After being exposed to Poirot, both Dr. Gerard and Dame Westholme committed suicide after biding goodbye with their daughter. In the original novel, Dr. Gerard remained alive and had no participance to the murder.