So what happened to make Lady Dedlock finally leave her loving husband and comfortable home, and abandon her place in society?

While Sir Leicester was lying forgotten on the floor of his library, in another part of the Dedlocks' London house My Lady was talking to Mrs Rouncewell, the housekeeper from Chesney Wold.

'Mrs Rouncewell,' said Lady Dedlock in surprise, 'what are you doing in London? Has something happened? What is the matter? Tell me, please.'

'Trouble, My Lady. Sad trouble. Friends of my younger son sent for me and I came immediately,' Mrs Rouncewell explained. 'I have seen George after all these years - he is in custody for the murder of Mr Tulkinghorn. My Lady, I have a letter that was delivered to me last night at Chesney Wold. I have not spoken of it to anyone. Please read it after I have gone; then, if you pity him, please help him. Without a doubt, my son is innocent.'

After the housekeeper left, Lady Dedlock opened the letter and saw a newspaper report of the death of Mr Tulkinghorn. At the bottom of the page was her own name with the word MURDERER written beside it.

Then, without warning, a servant told My Lady that Mr Guppy was at the door and wished to speak to her.

Mr Guppy had a short message: 'Madam, Captain Hawdon's packet of letters was not burned with Mr Krook, but was found in Tulkinghorn's office after his death. The letters will not stay secret for much longer.'

Alone, Lady Dedlock knew that she would never escape her past, even with Mr Tulkinghorn dead. In a rush she wrote this letter to her husband and left it on her table before hurrying out of the house:

Please believe me: I am innocent of the murder of Mr Tulkinghorn. I am guilty of everything else that people will tell you. Tulkinghorn said that he would tell you everything, so I followed him on the night of his murder. I wanted to stop him from ruining our life together. I found his house dark and silent. I rang twice at his door, but there was no reply and I came home.

Please forget me. I am afraid that you have wasted your love and care on me. I am leaving so my past does not bring disgrace on you and your family. This is my final goodbye to you.

She dressed quickly, covered her head with her veil and left all her jewels and money behind. She listened, went downstairs when the hall was empty, opened into the cold wind and shut the great door and escaped.

***