The film begins on June 1, 1972. The film opens on a triumphant President Nixon arriving at the Capitol to address a joint session of Congress. He is at the height of his popularity and he seems unstoppable.
The film then cuts to an underground parking garage at the Washington D.C. Watergate complex, where a security guard notices a door ajar and finds that it's been tampered with tape to keep it open. He calls security who catch five buglers breaking into the Democratic National Committee office in the complex.
We cut to The Washington Post's headquarters where editor Harry Rosenberg gives the freshman reporter Bob Woodward the task of investigating the break-in, which is mysterious because all of the burglars were loaded with cash with sequential serial numbers. He visits the courthouse where five men are on trial, and even though they have no apparent connections, they somehow have their own council. Woodward learns that one of the burglars used to work for the CIA, alerting his suspicions. Through a tip, he finds out that the burglars had a phone number to the White House and the initials of Howard Hunt in his bag. Woodward uses his contacts to discover that there is a link between the burglars and the White House.
Woodward is assigned a partner on the Watergate story: Carl Bernstein. Bernstein is pushy and aggressive and the two begin at odds. Woodward even finds that Bernstein has stolen one of his stories and rewritten it. Woodward realizes that Bernstein is talented, but chastises him for not being collaborative.
Woodward contacts an old administration official who becomes an informant from within the administration. This person is only known as "Deep Throat." Deep Throat communicates with Woodward through code in order to set up meetings, and they meet in dim parking garages. His advice: "follow the money."
By following the money, Bernstein finds himself at the Miami district attorney's office. After being ignored for an entire day, Bernstein forces his way in to see the DA, where he finds a check connecting money given to the burglars to staff at the Committee to Re-Elect the President (CREEP). This organization, run by Nixon's formal attorney general, seems to be connected to the administration. Upon investigating, the duo finds that many of the people writing checks are simply donors who have given money to the organization, but they do not know what is done with it. They come to find that CREEP acts as a slush fund, moving money around to different undisclosed people.
The paper's editors don't find the story convincing. Why would Nixon, a surefire win in November, be hiring people to break into the Democratic National Committee? However, executive editor Ben Bradlee believes in the team, and allows them to keep publishing stories.
Through their investigations, they find that this slush fund was used to sabotage Nixon's opponents. An accountant for CREEP confirms that the fund is upwards of 6 million dollars. A California man, Segretti, admits to being paid to travel the country and sabotage Democratic campaigns in the primaries ("rat-fucking") to ensure the President's election. Hugh Sloan, a treasurer for CREEP, admits that five men control the slush fund, many of them directly linked to the Nixon administration.
Bernstein is able to connect the slush fund to H.R. Haldeman, one of Nixon's aides. Upon Bradlee asking him to confirm the story, he mischaracterizes a source, causing the paper to run a story that the sources deny. This is a big setback, however, Bradlee does not fire or take Bernstein and Woodward off the story.
Woodward oversleeps for his final meeting with Deep Throat. When he arrives, he explodes at him: "I'm tired of your chickenshit games. Tell me what you know!" Deep Throat confesses that this Watergate coverup is a conspiracy that goes throughout the intelligence agencies in the government. He also says explicitly that Woodward and Bernstein's life might be in danger.
Woodward goes to Bernstein's house, putting on music in case they are bugged. He explains what Deep Throat has told them, and the pair goes to Bradlee's house. Bradlee tells them to prepare for what's to come, even though they made a mistake. He believes in the story and is in it for the long haul.
Nixon wins reelection and is sworn in as Woodward and Bernstein continue thier dilligent work. Though it seems as though Nixon has won, the headlines they type show all the president's men getting prosecuted in a short period of time for their hand in the illegal activity surrounding Watergate until finally Nixon resigns, and Gerald R. Ford becomes the President of the United States.