Read it through once

The Sheep of the prisons turned from him to Sydney Carton, and said, with more decision, “It has come to a point. I go on duty soon, and can’t overstay my time. You told me you had a proposal; what is it? Now, it is of no use asking too much of me. Ask me to do anything in my office, putting my head in great extra danger, and I had better trust my life to the chances of a refusal than the chances of consent. In short, I should make that choice. You talk of desperation. We are all desperate here. Remember! I may denounce you if I think proper, and I can swear my way through stone walls, and so can others. Now, what do you want with me?”