Returning to the night in 1936 when he, Willie, and Sugar-Boy drove away from Judge Irwin's house, Jack reflects that his inquiry into Judge Irwin's past was really his second major historical study. He recalls his first, as a graduate student at the State University, studying for his Ph.D. in American History. Jack lived in a slovenly apartment with a pair of slovenly roommates, and blew all the money his mother sent him on drinking binges. He was writing his dissertation on the papers of Cass Mastern, his father's uncle.
As a student at Translyvania College in the 1850s, Cass Mastern had had an affair with Annabelle Trice, the wife of his friend Duncan Trice. When Duncan discovered the affair, he took off his wedding ring and shot himself, a suicide that was chalked up to accident. But Phebe, one of the Trices' slaves, had found the ring, and taken it to Annabelle Trice. Annabelle had been unable to bear the knowledge that Phebe knew about her sin, and so she sold her. Appalled to learn that Annabelle had sold Phebe instead of setting her free--and appalled to learn that she had separated the slave from her husband--Cass set out to find and free Phebe; but he failed, wounded in a fight with a man who insinuated that he had sexual designs on Phebe. After that, he set to farming a plantation he had obtained with the help of his wealthy brother Gilbert. But he freed his slaves and became a devout abolitionist. Even so, when the war started, he enlisted as a private in the Confederate Army. Complicating matters further, though a Confederate soldier he vowed not to kill a single enemy soldier, since he believed himself already responsible for the death of his friend. He was killed in a battle outside Atlanta in 1864. After leaving to find Phebe, he had never set eyes on Annabelle Trice again.
One day Jack simply gave up working on his dissertation. He could not understand why Cass Mastern acted the way he did, and he walked away from the apartment without even boxing up the papers. A landlady sent them to him, but they remained unopened as he endured a long stretch of the Great Sleep. The papers remained in their unopened box throughout the time he spent with his beautiful wife Lois; after he left her, they remained unopened. The brown paper parcel yellowed, and the name "Jack Burden," written on top, slowly faded.
This chapter is mostly occupied with the Cass Mastern episode, which is one of the most difficult and complex inclusions in the novel. On the surface, the Cass Mastern episode seems completely irrelevant to All the King's Men--it does not affect the main characters of the novel, contains its own set of people and places, and is completely disconnected from the main plot. So why did Warren include it?
The answer is that the Cass Mastern episode is thematically important to All the King's Men, even if it is not important to the plot. Essentially, the story of Cass Mastern is the story of a man who commits an evil deed, and who finds the rest of his life shaped by his sense of responsibility for the outcome of that deed. Cass cannot simply forget about Duncan Trice and Phebe, and his sense of responsibility drives him to leave Annabelle, to try to free Phebe, and to become an abolitionist in the South, a very rare thing. The sense of responsibility Cass Mastern feels for Duncan Trice's death and the sale of Phebe is important, because the story of All the King's Men is in many ways the story of Jack Burden learning to accept responsibility for his own actions. Jack, like Cass, learns that consequences are real even within the tumult of history, which does not exist solely in his own mind.
As a young man, Jack is unable to understand Cass Mastern's motivations because he is not ready to confront the idea of responsibility--he still wants to evade his past, thwart his mother, and "escape the present," as he puts it. By the end of the novel, Jack writes that he "may now come to understand" Cass Mastern. Thus, the Cass Mastern story becomes a kind of index against which Jack's progress as a character can be measured. The closer Jack comes to understanding Cass Mastern, the closer he is to accepting the idea of human responsibility in time.