What is a summary of Crime and Punishment?

To summarize, the novel Crime and Punishment by Fyodor Dostoevsky is about how the mechanism of a person’s conscience as well as their beliefs about morality, humanity, and God can affect their subsequent actions and behavior. The novel explores the use of rationalization to justify a criminal act: murder. Finally, the novel also acts as a literary statement on how a capitalist system can influence some people to commit crimes like theft, prostitution and murder in order to survive.
The main protagonist is Rodion Romanovitch Raskolnikov, an ex-student and former teacher lamenting the fact that he is in debt to his landlord. He plans to pawn his father’s watch and then thinks of killing the pawnbroker, Alyona Ivanovna, and stealing her possessions. However, Raskolnikov begins to suffer psychologically from the first moment he thinks of committing the murder, as he is unsure of whether or not he can even go through with it:

And how could such an atrocious thing come into my head?  What filthy things my heart is capable of.

When Raskolnikov discovers his sister, Dounia, is planning to marry a man named Pyotr Petrovitch Luzhin, he gets upset, believing Dounia’s motivation to get married is purely financial, thus, giving him more of a rationalization for murdering the pawn broker and stealing her things.
Raskolnikov further rationalizes the homicide by believing all of the many bad deeds Ivanovna has done outweighs Raskolnikov’s single bad deed:

“When reason fails, the devil helps!” Raskolnikov thought with a strange grin.

Raskolnikov eventually does decide to go through with the murder, borrowing an axe to kill Ivanovna. However, Ivanovna’s sister, Lizaveta, walks in on him, and he kills her as well. He then clumsily tries to cover up the evidence.
Raskolnikov’s guilt manifests in various ways. He becomes physically ill and feverish. He entertains suicidal thoughts for a time. His energy level plummets and he frequently succumbs to exhaustion. He acts strange in front of his family members and in front of Porfiry, a police officer who suspects Raskolnikov is the killer.
Raskolnikov’s rationalization for his actions is further illuminated when Porfiry discovers an old article authored by Raskolnikov in which he argues that any crime or any transgression may be justified if the person committing the crime is deemed extraordinary:

I don’t contend that extraordinary people are always bound to commit breaches of morals, as you call it. I simply hinted that an extraordinary man has the right, that is not an official right, but an inner right to decide in his own conscience to overstep certain obstacles, and only in case it is essential for the practical fulfillment of his idea.

Though Raskolnikov succeeds in stopping Dounia from marrying Luzhin, he witnesses a tragic event and eventually succumbs to the pangs of his conscience and turns himself in to the police. He is sentenced to seven years in Siberia, but he remains hopeful he can start a new life when he gets out. 
http://community.middlebury.edu/~beyer/courses/previous/ru351/novels/cp/CPstudy.shtml