Charles Cartwright

In the novel Three Act Tragedy, Sir Charles Cartwright is a well-known stage actor, and Poirot's assistant in his investigations.

Sir Charles is described as an "extraordinarily good-looking man, beautifully proportioned, with a lean humourous face". He is fifty-two years old, with a touch of grey at his temples. Acting is second nature to him, such that he is always acting, even in his private life. Two years before the events of the novel, he retired from the stage, saying he wanted to live a simple country life, and indulge his old fancy for the sea. He moved to Loomouth, and built Crow's Nest.

Sir Charles is in love with Hermione "Egg" Lytton Gore.

Role in the novel (it contains several spoilers)
At the beginning of the novel, Sir Charles hosts a house party at Crow's Nest. When the guests arrive, he mixes cocktails, and Temple serves them to the guests. When Rev Stephen Babbington is suddenly taken ill and dies after drinking one of the cocktails, Sir Charles suspects that he has been murdered. However, an analysis of the cocktail glass finds nothing, and the verdict given at the inquest was death by natural causes.

When Sir Bartholomew Strange dies under similar circumstances, Sir Charles begins to investigate. He and Mr Satterthwaite go to Strange's home, Melfort Abbey, and interview the domestic staff.

Sir Charles, Mr Satterthwaite and Egg assist Poirot in the investigation, by visiting the suspects who were present at both Crow's Nest and Melfort Abbey. Sir Charles interviews Muriel Wills, and learns that the butler at Melfort Abbey, Ellis, had a birthmark on his wrist. He and Egg also visit Mrs Babbington and Mrs Milray.

After their visit to Mrs Milray, Sir Charles and Egg declare their love for each other. He also reveals to Egg that his real name is Charles Mugg.

Sir Charles later attempts to get a second interview with Muriel Wills, but is told that she had left home that morning, and had sent word that she would not be back for a few days.

It is later revealed that Sir Charles had gotten married when he was young, before he became a well-known actor. His wife was in an asylum, and so he could not divorce her. Sir Bartholomew was the only person who knew of this. Sir Charles wanted to marry Egg, but he knew that Sir Bartholomew would not allow that. So, he planned to poison Sir Bartholomew.

Sir Charles extracted pure nicotine from rose spraying solution. He put some into one of the cocktail glasses, making sure that neither he nor Egg took that glass. He also knew that Sir Bartholomew would not take it, as he never drank cocktails. This was a dress rehearsal for the murder of Sir Bartholomew.

After the death of Stephen Babbington, Sir Charles posed as Ellis at Melfort Abbey. Sir Bartholomew knew about this, and it was a joke between them, or possibly a wager. Sir Charles put nicotine in Sir Bartholomew's port glass. When Sir Bartholomew collapsed, and everyone's attention was diverted, Sir Charles switched the glass for a different one.

As part of his disguise as Ellis, Sir Charles painted a birthmark on his wrist, which Muriel Wills noticed. When she saw Sir Charles after that, she realised that his hands were the same as the hands she had seen on Ellis. Sir Charles felt that she suspected him, so he went to see her on the grounds that he wanted a second interview. However, she had left home on Poirot's advice, and was in hiding.

Sir Charles also sent a box of liqueur chocolates to Mrs Margaret de Rushbridger. The chocolates were laced with nicotine. He had sent a telegram to Poirot in her name, saying she could give important information about Sir Bartholomew's death. This was to divert suspicion from himself. However, Mrs de Rushbridger would have told Poirot that she knew nothing about Sir Bartholomew's death, so he killed her to prevent that from happening.

Portrayals
In Murder in Three Acts (1986), the part of Charles Cartwright was played by Tony Curtis. Instead of a famous British stage actor, here he is an American and a Hollywood star. The motive for the murders are changed in this version and follows that in the very first U.S. edition of the novel published in 1936. Here, Cartwright was himself suffering from psychosis and mental breakdown. Dr Strange knew about this and had been treating him. Cartwright murdered Strange to prevent the doctor from putting him away into an asylum.

In the film adaptation of Three Act Tragedy in Series 12 of ITV's Agatha Christie's Poirot drama series, the part of Charles Cartwright was played by Martin Shaw.