What is the main problem in a tale of 2 cities?

What is da main problem in a tale of 2 cities?
Plzz answer!!!

First of all, is this some homework you're trying to weasel your way out of? because if that's the case, you really should read the book.
I just did a quick Google on the title, and got this from Wikipedia.org:

A Tale of Two Cities (1859) is a novel by Charles Dickens, set in London and Paris before and during the French Revolution. With 200 million copies sold, it is the most printed original English book, the most printed and among the most famous works of fiction.[1]

It depicts the plight of the French peasantry under the oppression of the French aristocracy in the years leading up to the revolution, the corresponding brutality demonstrated by the revolutionaries toward the former aristocrats in the early years of the revolution, and a number of unflattering social parallels with life in London during the same time period (hence the work's title). It follows the lives of several protagonists through these events, most notably Charles Darnay, a French once-aristocrat who falls victim to the indiscriminate wrath of the revolution despite his virtuous nature, and Sydney Carton, a dissipated British barrister who endeavours to redeem his ill-spent life out of love for Darnay's wife, Lucie Manette.

Look it up on Wiki yourself, and there's a lot of links to follow.
(By the way; The title should be written A Tale Of Two Cities. The 2 makes you look like you're 9 years old.