What is each of the four sections of In Cold Blood by Truman Capote about?

In Cold Blood by Truman Capote is a narrative history about the murder of the Clutter family in Holcomb, Kansas in 1959. In the first part, "The Last to See them Alive," Capote describes the members of the Clutter family, a prosperous and devout farm family. Herb, the father; Kenyon, the son; Nancy, the daughter; and Bonnie, the mother (who is confined to her bed with a nervous disorder). Two older daughters are married and live away from home. The section also contains a description of the murderers, Perry Smith and Richard "Dick" Hickock. They were recently released from jail in Kansas, and one of Dick's cellmates had told him about Herb Clutter and had misinformed him that Herb kept a great deal of money in his house. At the end of the section, the killers arrive at the Clutter's house, and the bodies are discovered in the morning. Capote does not describe the murders in the first section.

In the second section, "Persons Unknown," the chief inspector involved in the murder, Alvin Dewey, tries to put together the confusing clues. While the murders seem to have been motivated by robbery, less than $50, a pair of binoculars, and a portable radio were taken. Bonnie and Nancy Clutter were tied up and tucked into their beds, and the son, Kenyon, rested on a pillow before being shot in the face. The father, Herb, had his throat slit, and his body rests on a mattress box. The community presses Dewey to arrest a suspect, but the crime continues to confound the authorities. Perry Smith and Dick Hickock have now escaped to Mexico, and Capote describes Smith's childhood in graphic detail using letters and articles from his childhood that Smith is deciding whether to keep or jettison. Smith had a horrendous childhood, as his mother was an alcoholic, his brother and sister killed themselves, and his father roamed around and prevented Smith from getting much of an education. He was raised partly in orphanages, where he was routinely abused.

In the third section, "The Answer," Hickock's former cellmate, Floyd Wells, tells authorities that he suspects Smith and Hickock of the murders. Wells had told Hickock that Clutter was a prosperous farmer with a safe in his house. Smith and Hickock have run out of money and return to Kansas to pass bad checks. They are picked up in Las Vegas, and Hickock immediately confesses to the crime (and Smith follows suit). They explain that they murdered the family intending to get money and killed them to avoid having any witnesses left alive. Hickock had planned to rape Nancy, but Smith had prevented him. Smith, incensed and in a rage after seeing Hickock's intention to rape the girl, slit Herb Clutter's throat. It is Clutter's success and sanity that enrage Smith. 

In the fourth section, "The Corner," the two killers are taken to separate prison cells, where they fight about the confession. Smith wants to confess to all four murders to soothe Herb's mother, whom he likes. Dr. Jones, a court psychiatrist, evaluates them to assess their sanity, and they describe their childhood to him in writing. Smith's childhood is retold in detail, but they are declared sane enough to have known right from wrong. They are found guilty and are given the death penalty. After being transferred to death row, "the Corner," Hickock mounts a successful attempt to get an appeal. Capote describes the other inmates on death row. Eventually, their appeal exhausted, they are executed in 1965.