The use of foreshadowing is key in Chapter 6 of Book II as on a Sunday afternoon, Charles Darnay tells Lucie that workmen have come upon the cell in which her father, Dr. Manette, has been imprisoned; they find the letters "D.I.G."
After this remark, Manette becomes disturbed, but recovers. Miss Pross brings tea, and Sydney Carton "lounges" in, but there are no "hundreds of people" visiting as Miss Pross has complained earlier. Later, Lucie, Darnay, and Carton lean against a window, gazing into the "heavy twilight" : "They spoke low, as people watching and waiting mostly do...as people in a dark room, watching and waiting for Lightning, always do."
Adding to Darnay's comment of hearing the footsteps of those coming into their lives, Sydney Carton says, "There is a great crowd coming one day into our lives....I take them into mine!" Lucie echoes his presentiment: "I have imagined them, the footsteps of the people who are to come into my life, and my father's."
Later Mr. Lorry remarks to Jerry Cruncher, the graverobber, "What a night...to bring the dead out of their graves."
Clearly, as one editor has already pointed out, the footsteps foreshadow the French Revolution. But, the remarks of Lucie and Sydney Carton also predict the direct involvement that these characters will later have in the death that the revolution brings.
http://www.enotes.com/a tale of two cities
Lucie states that she believes they represent the footsteps of all the people who have come and gone in their lives, for good or ill. Though "A Tale of Two Cities" does not have the huge cast of characters as do most of Dickens's other novels, there are still many people who have some effect on the lives of the main characters. Darnay, however, says, "A multitude of people, and yet a solitude!? To him, the footsteps emphasize his loneliness, since no footsteps approach specifically for him.
The footsteps also represent the approach of doom. Earlier it states thatpeople were "speeding away to get shelter before the storm broke." This "storm" can be interpreted as the approach of the French Revolution, in which the characters will be caught up.
if these are the footsteps echoes that lucee mentioned :) then it means that the revolution started in france and is going towards england and that will affect lucee and her family (charles dickens is adding hints to predict what is going to happen and add curiosity to the reader)and he is foreshadowing that it will be a big revolution that many people will be killed in it and many will end insane because of what they will lose
Dickens uses the footsteps to foreshadow(to give hints to add curiosity to the reader) the hundred of footsteps of the revolution that will soon occur in Paris. He is foreshadowing the many lives that will be lost and all the people who'll end up lonely in the revolution soon to come in Paris.