Jane Wilkinson, Lady Edgware is one of the main characters of the novel Lord Edgware Dies. She is a talented young American actress very well-known in London, who has starred alongside Bryan Martin in several films. Arthur Hastings has always been a great admirer of her acting. Poirot, however, says that her quality at acting depends on the role--if she was to be the center of the play of film, she would play her part very well. However, she could have not played a minor character part adequately.
She was described as having a "well known, slightly husky voice", and a "delightful husky laugh". Three years prior to the opening of the novel, she married the wealthy George Alfred St Vincent Marsh, better known as Lord Edgware. Rumours said she left him shortly afterwards--indeed, they did not live in the same house.
One evening, Hastings and Poirot meet her, Bryan Martin, Carlotta Adams and Ronald Marsh in a theatre. After some background given to the reader by Poirot, Jane asks to talk with him in private. She tells him she needed to "get rid of her husband". She said she consulted several lawyers, but none of them could provide a solution to the problem. Poirot asks her about the reason of her wanting to divorce her husband, and that is, because she wanted to marry someone else. That was the Duke of Merton, to the surprise of Hastings who thought of him like a man whose life was austere in the extreme.
Bryan Martin told Poirot that Lady Edgware could kill someone quite cheerfully, despite the fact that she "did not have the brains for murder" and would be instantly caught. Poirot himself says she has "the brains of a rabbit": she does not know anything about history or geography, and "the name of the playwright Molière could suggest her a maison de couture".
Plot [SPOILERS AHEAD]
Some days later Lord Edgware was murdered. She was the prime suspect, and the secretary Miss Carroll sworn she saw Jane entering the study at 10 o'clock, and kept that version of the story even after Poirot proved she was on the staircase so she could not see her face properly. The newly hired butler Alton saw it as well, despite having seen her only once or twice.
On the night of Lord Edgware's murder, Jane claimed she was having dinner at Sir Montagu Corner's. This was confirmed by Corner, Donald Ross, and several other guests, which removed her from the suspect list. The woman seen by Miss Carroll was Carlotta Adams in disguise, which was subsequently killed to avoid her revealing the identity of the person who hired her to frame Lady Edgware. This seems further confirmed by the fact that she never wore black, and the woman impersonating her was completely dressed in black.
She told the police that, when dining at Chiswick, she received a strange telephone call. The person speaking asked if she was Jane Wilkinson, does not say anything else after receiving the answer, and rings off. At a second dinner party, someone uttered something about "the judgement of Paris" and Jane replied with "Paris? Why, Paris doesn’t cut any ice nowadays. It’s London and New York that count". After that, Donald Ross rings Poirot up to tell him somehting about that and gets stabbed.
All the questions that tormented Poirot later were resolved. Afterall, it was indeed Jane who killed Lord Edgware, Carlotta and Donald Ross. The woman claiming to be her, the one which was seen by Alton and Miss Carroll, was indeed Jane. Carlotta goes to the dinner party disguised as Lady Edgware, without knowing what would have happened next. Before dying, she wrote a letter to her sister Lucie, in which she stated that the person who hired her to pose as Lady Edgware was Ronald Marsh. It later turns out that one page was taken, and a letter was torn out to change "she" to "he".
However, Donald Ross spotted the fake. The woman at the dinner at Chiswick knew a lot about Greek mythology, so it was impossible for the woman that was so informed about that be so ignorant about "the judgement of Paris" days later.
At the end of the novel, Hastings returns to the Argentine and receives a manuscript from the killer explaining the motive: divorcing Lord Edgware would have been of no use, because the Duke of Merton was a catholic.