Nothing but the Truth is a drama film. The inspiration for the screenplay was the case of journalist Judith Miller, who in July 2005 was jailed for contempt of court for refusing to testify before a federal grand jury investigating a leak naming Valerie Plame as a covert CIA operative, but this was merely a starting point for what is primarily a fictional story.
In Washington, D.C., a female reporter faces a possible jail sentence for outing a CIA agent and refusing to reveal her source. Rachel Armstrong (Kate Beckinsale) is an ambitious reporter for the Capital Sun-Times. When she discovers fellow soccer mom Erica Van Doren (Vera Farmiga) is working as a covert operative for the CIA and recently returned from Venezuela, where she was investigating an assassination attempt on the President of the United States, she confronts her and requests confirmation. Erica refuses to cooperate, but Rachel has no doubts about the veracity of the report, and her story becomes front-page news with the support of editor Bonnie Benjamin (Angela Bassett) and Avril Aaronson (Noah Wyle), who serves as the newspaper's legal counselor.
Because revealing a covert operative's identity is a treasonous offence and because the individual who leaked the information to Rachel is a potential threat to national security, special Federal prosecutor Patton Dubois (Matt Dillon) convenes a grand jury and demands to know who her source is, information she refuses to divulge. High profile attorney Albert Burnside (Alan Alda), hired by the newspaper to defend Rachel, is certain his personal friendship with Judge Hall will facilitate matters and is shocked when his client is jailed for contempt of court.