While reading The New York Times, Truman Capote is riveted by the story and calls The New Yorker magazine editor William Shawn to tell him that he plans to document the tragedy.

The Deweys, Lee, and Capote are having dinner when the murder suspects, Perry Smith and Richard "Dick" Hickock, are caught.

Flattery, bribery, and a keen insight into the human condition facilitate Capote's visits to the prison where the accused are held.

Following the trial and conviction, after which both Smith and Hickock are sentenced to death, Capote gains continued access to the murderers by bribing Warden Marshall Krutch.

Capote spends the following years regularly visiting Smith and learning about his life, excepting a year-long stint when he goes to Morocco and Spain to write the "first three parts" of the book, accompanied by his romantic partner Jack Dunphy.

Though initially an effort to provide proper representation and extend Capote's opportunity to speak with the killers, the appeals process drags on for several years.

Without the court case being resolved, Capote feels he is stuck with a story without an ending and is unable to complete his book.

Lee's best-selling novel To Kill a Mockingbird is turned into a movie, but Capote is unable to share in the joy of his friend's success, too caught up in drinking through his misery.

A textual epilogue notes that In Cold Blood made Capote the most famous writer in America; that Capote never finished another book, dying in 1984 from complications due to alcoholism; and that he chose a quote from Saint Teresa of Ávila – "More tears are shed over answered prayers than unanswered ones"[3][4] – as the epigraph for his unfinished final novel.

The site's consensus reads: "Philip Seymour Hoffman's riveting central performance guides a well-constructed retelling of the most sensational and significant period in author Truman Capote's life.

[21] No non-fiction sources (including Clarke's) assert that Capote attempted to secure legal representation for Smith and Hickock as is shown in the film.

[20] Capote mainly corresponded with Hickock and Smith through letters, visiting them in person fewer than half a dozen times.