Answer:
A story about a prisoner discretely leaving an instruction on the floor whilst in prison.
Dr Mannete was deeply troubled and startled by the story.
Step-by-step explanation:
A couple of months after his acquittal from his trial in court, Charles Darnay decides to pay the Manettes a visit at their home in Soho, France.
Whilst discussing, Darnay related a story he heard on a recent trip to the Tower of London where a prisoner discretely left an instruction by writing the inscription 'D.I.G' on the floor of the prison house.
Charles Darnay went on to say that years later when the ground underneath the inscription 'D.I.G' was dug up, an old leather suitcase with the ashes of a letter was found.
Dr Manette did not receive the story very well. He was startled and his face became very pale as if he was not feeling well. Clearly, the story struck a wrong chord with him as it reminded him of events while he was imprisoned.