In 1991, Out of the Past was added to the United States National Film Registry as being deemed "culturally, historically, or aesthetically significant."
The film is considered by film historians to be a superb example of film noir, due to its convoluted, dreamlike storyline and its chiaroscuro cinematography (cinematographer Nicholas Musuraca also shot Tourneur's Cat People).
Before he leaves, Jeff begins to tell Ann about his mysterious past. His real name is Jeff Markham. He and partner Jack Fisher (Steve Brodie) worked as private investigators in New York. They took on a job for a rich gambler, Whit Sterling (Kirk Douglas). The movie then flashes back to that time.
Sterling hires Jeff to find his girlfriend, Kathie Moffat (Greer). She had run away after shooting Sterling and stealing $40,000 from him. He wants her and the money returned. Jeff talks to Kathie's former maid, Eunice (Theresa Harris). He learns that she had packed for warm weather, was vaccinated, and left for Florida. Jeff knows that vaccinations aren't needed for Florida, but they are for Mexico. He tracks the luggage to Mexico City and learns that she had been there. From there, the trail leads to Acapulco.
Jeff finds Kathie there. At first he doesn't tell her that he's been hired to find her. Later, when he goes to send a telegram to Whit, he finds the Western Union office closed for the siesta. So instead, he sees her again and they begin to fall in love. He tells her the truth, that Whit is alive and just wants her back. She claims that she didn’t take Whit’s money. Eventually, they decide to run away together. They plan to start from Jeff’s hotel the next morning.
However, Whit and his henchman Joe Stephanos (Paul Valentine) show up unexpectedly, having flown down to check up on Jeff. He tells Whit that he hasn’t found Kathie yet, that she has caught a boat south. After Whit leaves, the lovers take a boat north.
They live as inconspicuously as possible in San Francisco, fearful of being found but thinking the odds are one in a million that anyone will spot them. But it happens. Fisher, Jeff’s old partner, spots him at a race track. Tracking the couple to a cabin in the woods, he demands the $40,000 in return for his silence. A fistfight breaks out that ends when Kathie fatally shoots the would-be blackmailer. She then drives off, leaving Jeff behind. He finds her bank book and discovers a balance of $40,000.
The movie then flashes forward to Jeff and Ann. He tells her that he never saw Kathie again, and that he has to tell Whit all that has happened. He arrives at Whit’s place and sees that Kathie is living with him again. Rather than discussing the past, Whit says he wants to hire Jeff to recover some income tax records that a lawyer, Leonard Eels (Ken Niles), is using to blackmail him. Jeff agrees to take the job.
In San Francisco, Jeff meets Eels' secretary, Meta Carson (Rhonda Fleming). She tells him of her and Whit's plan to get the papers. When Jeff meets Eels, he warns him that Whit isn't interested in paying Eels off, and that he should give up the papers. He returns later, only to find Eels dead. With Kathie's help, Whit had planned the murder of Eels and hoped to frame Jeff for it. Jeff also learns that Kathie told Whit that it was Jeff who killed his ex-partner Fisher, and that among Eels' papers is an affidavit she signed naming Jeff as the killer. Jeff goes to Whit’s night club, slugs the manager and takes the tax papers. He tries to trade them for the affidavit, but that arrangement goes awry.
Later, when Jeff again tries to meet with Whit, he finds that Kathie has killed him. She tells Jeff that he must leave with her or be arrested for killing Fisher, Eels and now Whit. Jeff agrees, but when she goes to get her bags, he makes a phone call. They leave together, but soon come upon a police roadblock. Kathie realizes Jeff has double-crossed her. She shoots and kills him, calling him “a dirty, double-crossing rat.” The police then fire on their car, killing both Kathie and Jeff.
The staff at Variety magazine liked the acting in the drama and wrote, "Out of the Past is a hardboiled melodrama [from the novel by Geoffrey Homes] strong on characterization. Direction by Jacques Tourneur pays close attention to mood development, achieving realistic flavor that is further emphasized by real life settings and topnotch lensing by Nicholas Musuraca...Mitchum gives a very strong account of himself. Jane Greer as the baby-faced, charming killer is another lending potent interest. Kirk Douglas, the gangster, is believable and Paul Valentine makes role of henchman stand out. Rhonda Fleming is in briefly but effectively.
More recently, film critic Roger Ebert wrote, "Out of the Past is one of the greatest of all film noirs, the story of a man who tries to break with his past and his weakness and start over again in a town, with a new job and a new girl. The movie stars Robert Mitchum, whose weary eyes and laconic voice, whose very presence as a violent man wrapped in indifference, made him an archetypal noir actor. The story opens before we've even seen him, as trouble comes to town looking for him. A man from his past has seen him pumping gas, and now his old life reaches out and pulls him back.
The review aggregator Rotten Tomatoes reported that 96% of critics gave the film a positive review, based on 23 reviews.