The title of "Truth," a gripping, beautifully executed journalistic thriller about the events that ended Dan Rather’s career as a CBS anchorman, should probably be appended with a question mark. More than most docudramas about fairly recent events, it is so well-written and acted that it conveys a convincing illusion of veracity.

Just as there are conspiracy theorists who will never be satisfied with the Warren Commission report on the Kennedy assassination, there are some who passionately believe that Rather and his producer Mary Mapes (Cate Blanchett) conspired to tarnish George W. Bush’s reputation.

The Sept. 8, 2004, episode of "60 Minutes II" alleged that family connections enabled Bush to avoid the draft in the Vietnam era by serving in the Texas Air National Guard. After Mapes’ failure to authenticate documents indicating that Bush, during his term of National Guard service, was lax in his duties and went missing, she was fired, and Rather stepped down as anchorman.

Their defenders believe that Rather and Mapes and her team were fed to the wolves for political reasons. The movie insinuates that CBS, to avoid further embarrassment and to curry favor with conservatives should Bush win the election, allowed it to happen. "Truth" doesn’t voice an opinion, and none of its characters expresses political beliefs even in private. Still, its treatment of Rather, who exudes the stately aura of a grand old man, and Mapes, who was a kind of surrogate daughter, makes it perfectly clear whose side it takes.

Rather’s exit from the anchorman job at CBS, of course, was less momentous than a presidential assassination. But because it coincided with the run-up to a presidential election, it was potentially very consequential. At the time the story aired, Bush was a little bit ahead of John Kerry, the Democratic presidential nominee, in the polls and the "swiftboating" campaign to discredit Kerry’s military record had already begun.

The movie, written and directed by James Vanderbilt, who is best known as the screenwriter of "Zodiac," focuses not on Rather, who is played with a dignified folksiness by Robert Redford, but on Mapes, whose 2005 book, "Truth and Duty: The Press, the President, and the Privilege of Power" is the basis for the movie.

"Truth," which tells Mapes’ side of the story, is sympathetic, but doesn’t try to exonerate her. Blanchett, in one of her greatest screen performances, offers a compelling portrait of a driven, high-strung television journalist fearlessly operating in a cutthroat professional climate. She is relentless in tracking down documents that appear to have been written in the early ’70s by Bush’s commander, Jerry B. Killian, who died in 1984. And when she finally secures an interview with Lt. Col. Bill Burkett (Stacy Keach), an ailing National Guard veteran, who produces incriminating documents that seem to be authentic, her case momentarily seems airtight.

"TRUTH" Rated: R Opens today

The explosive reaction to the story, once it is broadcast, turns "Truth" into a suspenseful detective story in which the minutiae of typewriters, typefaces and word-processing technologies are explored with an increasingly frantic sense of desperation.

The most colorful member of Mapes’ crack team of researchers and interviewers is Mike Smith (Topher Grace), an impatient firebrand with a very short fuse. Other team members include Lt. Col. Roger Charles (Dennis Quaid), a military consultant who worked with Mapes on the program’s Peabody Award-winning piece about Abu Ghraib, and Lucy Scott (Elisabeth Moss, underused), a Texas journalism professor.

Mapes is the heart and soul of "Truth." The family breadwinner, she lives in Dallas with her husband, Mark Wrolstad (John Benjamin Hickey), and young son. Blanchett plays her as fiery-eyed go-getter who pursued the story with a dogged ferocity. Her eyes flashing, she describes a tip linking Bush to the bin Laden family that went nowhere as "a juicy piece of brisket."

The screenplay brings in her bitter relationship with her abusive father, whose unkind words about her after the scandal breaks incite savage, profane invective from the right-wing bloggers who call her "feminazi" and "witch." Mapes has a thick skin but not so thick that she isn’t wounded by her father’s public scolding and asks him to stop speaking out.

In a broader and sadder sense, "Truth" portrays network television news as a grim corporate culture obsessed with remaining above the political fray and maintaining an attitude of imperial detachment. Andrew Heyward (Bruce Greenwood), the president of CBS News from 1996 to 2005, is an unflappably cool operator who never raises his voice and maintains a chilly cordiality in the best of times that freezes into ice in the worst. In such a hypercompetitive environment, undercurrents of anxiety and tension of run deep. To combat the stress, a conspicuous amount of alcohol is consumed by both Rather and Mapes.

"Truth" doesn’t try to resolve mysteries that may never be solved or to drum up paranoia for the sake of extra heartbeats. But it still casts a pall of dread, an ominous sense that people in high places, whether in government or the news media, will stop at almost nothing to protect themselves and their interests. The retaliation against Mapes and her crew is similar to the smearing of the San Jose Mercury News journalist Gary Webb after his articles about cocaine smuggling and the funding of Nicaraguan rebels by the CIA. That story, told in Michael Cuesta’s "Kill the Messenger" (2014), a lesser film than "Truth," though still a powerful one, sends the same warning. Investigative journalism intended to upset the status quo can be dangerous and costly.

Just below the facade of professional decorum in "Truth" run deep currents of fear, suspicion and hatred. In the creepiest scene, Mapes is interrogated by a panel convened by CBS, whose members treat her with barely disguised contempt. When she eventually lashes out, she seals her own fate. It is a sad ending to a brilliant career.

© 2015 The New York Times Company