Who are the two men who demand that Dr. Manette accompany them and how are they related to Darnay? What is the result of this letter? (From Book 3 Chapters 6-10)

Manette was accosted in the street by what he perceived to be a pair of twins. They asked him to enter the carriage and showed him that they were armed. These men were serfs on the Marquis' lands (Darnay's uncle).