All the King's Men is narrated by Jack Burden, a young political muckraker for Willie Stark, governor of an unnamed Southern state in the 1930s. At its base, the novel is about Willie's rise to prominence and metamorphosis from a humble country lawyer to a fiery demogogue who uses corrupt means in order to do good for the poor masses of his state. It is also the complex story of Willie's downfall and the inextricable personal tale of Jack as the latter comes to realize his responsibility for the world around him.
The basic events of the novel are related with several flashback episodes, and all but the end of the last chapter is in the past tense, with the narrative being delivered from the perspective of Jack a few years after these events.
Willie, his wife Lucy Stark, his son Tom Stark, his bodyguard Sugar-Boy O'Sheean, his secretary and mistress Sadie Burke, his Lieutenant-Governor Tiny Duffy, and Jack travel to Willie's hometown of Mason City with a press junket in summer 1936, during Wililie's second term as governor. That evening, Willie and Jack drive to Burden's Landing, Jack's hometown, where they visit Judge Montague Irwin, a childhood father-figure of Jack's. Irwin has defied Willie politically, and Willie threatens to blackmail him. Jack receives the assignment to dig up dirt on the Judge.
In 1922, Jack, working as a journalist, is sent to cover Willie Stark, the Mason County Treasurer, who is being libeled out of office for defying local corruption. Stark loses his reelection race, but he is vindicated when a schoolhouse built by a corrupt contractor falls down, killing several children. Willie becomes a local hero in the countryside. Sadie Burke and Tiny Duffy, agents of a gubernatorial candidate trying to split the country vote, trick Willie into running for governor, and Jack is sent to cover Willie's campaign. Willie finds out about the ruse and reacts with defiance. He drops out of that race but begins to make fiery speeches, rallying the people of the countryside. In 1930, he runs for governor as a populist and wins. Meanwhile, Jack leaves his job and falls into a period of idleness he calls a "Great Sleep." He is awoken by Governor Stark, who hires him.
This chapter takes place sometime in 1933, during Willie's first term as governor. A corrupt member of Willie's cabinet is caught in a scandal, and Willie decides to protect him. The state legislature, enflamed by Willie's underhandedness and opposed to his wealth-sharing programs, begins impeachment proceedings, which Willie destroys by having Jack dig up dirt on individual lawmakers. During this period, Willie and his wife separate, Willie begins an extramarital affair with Sadie, and Jack grows closer to the governor and farther from his family and his concerned friends, Adam and Anne Stanton.
This chapter is primarily composed of a story within a story, the tale of Jack's Civil War-era ancestor Cass Mastern. The story is framed by Jack's experiences in graduate school, when he set out to write his thesis based on Cass's diary. Jack is unable to understand the motivations of his ancestor, and he abandons the project, consequently falling into his first Great Sleep.
This chapter resumes where the story left off at the end of Chapter One--with Willie's instruction to Jack to dig up dirt on Judge Irwin. Jack, using his considerable skill as an historical researcher, discovers that Judge Irwin had taken a bribe when he was the state Attorney General. This corruption resulted in a man's suicide. In addition, former governor Joel Stanton, father to Anne and Adam, had protected the Judge.
Willie moves forward with his plan to build a massive free hospital in the state, and he has Jack convince his childhood friend Adam Stanton to run it. Adam initially refuses on ethical grounds, but he relents when Jack shows him and his sister the evidence that their father committed an impropriety. Tiny Duffy tries to get Willie to give businessman Gummy Larson the contract to build the hospital (so that he can receive a kickback), but Willie balks. At last, Jack is told by an enraged Sadie that Willie and Anne were having an affair.
Jack is emotionally crippled by the revelation of the affair. He flees to the West Coast, where he divulges the story of his own love life, which began with his serious relationship with Anne back when he was in college, roughly 1920. The relationship ends as Anne realizes that the cynical and aimless Jack is still immature and unable to take responsibility in the real world. Afterwards, Jack drops out of graduate school and takes a job at a newspaper. Jack has one failed marriage that results in another Great Sleep. Back in the present, Jack theorizes that all humans are controlled by random impulses and that nobody has any responsibility for anything.
Cynical and numb, Jack returns to the capital, where a series of events threatens Willie's administration. First, Adam is bribed by an agent of Gummy Larson and then nearly quits. Second, Tom is accused of being the father of a child out of wedlock, and the issue is being used by his rival Sam MacMurfee. Willie has Jack use the dirt on Judge Irwin to force him to convince MacMurfee to back off. Jack visits the Judge, who refuses to be blackmailed. Shortly afterwards, the Judge kills himself, and Jack's mother reveals that Judge Irwin was his real father.
Because of the issue with his son, Willie begrudgingly gives the hospital contract to Gummy Larson. Shortly afterwards, Tom is rendered comatose by a football injury. After surgery is unable to relieve his son's condition, Willie has a change of heart and revokes the contract. Tiny Duffy, angered by this change, anonymously lets Adam know about the relationship between Willie and his sister. Adam assassinates Willie in the state capitol and is killed at the scene by Willie's security force.
Sadie tells Jack that she was the one who let Tiny Duffy know about Willie's and Anne's affair. Jack threatens Tiny Duffy, who has become governor, to go public with what he knows, but instead he decides to drop the matter. Tom has died, and Lucy has adopted the out-of-wedlock baby, whom she has named Willie. Jack's mother has divorced because of the death of her true love, Judge Irwin.
The end of the chapter is told in the present tense, from the year 1939. Jack is now married to Anne, has quit politics, and finally is completing his book about Cass Mastern.