After Cooper and Bergman scored in FOR WHOM THE BELL TOLLS at Paramount, this film was rushed into production in February 1943 and finished in late May. It was not released to the general public until after the end of WW II but had been seen for almost two years by members of the armed forces. It was one of several movies made but not released during the war by Warner Brothers. The others were DEVOTION, MY REPUTATION, and THE TWO MRS. CARROLLS, which didn't come out until 1947. Here, screenwriter Robinson took Ferber's best-seller, an essentially shallow romance novel, and adapted it well enough for the two stars to merit a huge box-office return for the time, upwards of $5 million. It's 1875 in New Orleans. Bergman is the half-Creole illegitimate daughter of a Louisiana man who'd slept with a local woman. After Bergman's mother's death, Bergman vowed to wreak havoc on her late father's family. Bergman sweeps into town from Paris with her bizarre retinue, which includes Austin, a dwarf, and Robson, a mulatto maid. Bergman is in the French market area near the docks when she meets Cooper, a lanky Texan. They flirt with each other, and Robson makes her feelings clear about what Bergman is doing. She'd prefer that her mistress stay away from this drawling gambler. Since New Orleans is such a small town, it's not long before tongues are wagging over their romance, essentially the same sort of malicious rumors which attended the love affair between Bergman's deceased parents. Cooper has to go north to Saratoga Springs on business and thinks this might be an opportunity to disengage himself from Bergman, whom he has correctly assessed to be a gold digger, although his heart is in her hands. Saratoga Springs was the watering hole for the wealthiest easterners of the era, and it isn't long before Bergman follows Cooper there with the express purpose of finding herself a rich man to marry. Upon arriving, Bergman pretends she is a rich French woman, carrying off the ruse with the $10,000 she's received from her father's snobbish family in return for leaving New Orleans. Bates, who knows everyone in Saratoga, is quick to spot Bergman as a phony. She checks up on Bergman's alleged background and confronts her with it, offering to arrange an introduction to Warburton, a big-bucks railroad man, in return for some cash if a marriage is made. Bergman refuses Bates and says she'll do it herself. Bates likes Bergman's spunk and tosses the money arrangement aside, agreeing to make the introduction anyway. Cooper observes all of this with some amusement but hates the thought of Bergman being so money hungry, especially since he does love her. Meanwhile, Cooper is involved in business with Warburton and some other wealthy men who hope to get control of the railroad to Saratoga (the Saratoga Trunk Line, hence the title) over a rival group. Austin becomes an aide to Cooper. There's a physical battle between the two groups during which Austin is hurt. Warburton's mother, Griffies, comes to Saratoga and doesn't believe a word of Bergman's background. But Bates speaks on Bergman's behalf, and Griffies is somewhat mollified. Warburton is not fooled by Bergman but loves her anyway and asks her to marry him. The battle between the two railroad groups winds up in a train crash, and Cooper comes back to town with Austin in his arms just as Bergman and Warburton are about to announce their marriage at a fancy-dress ball. Upon seeing Cooper, who was also injured, Bergman forgets about her arranged romance with Warburton and races to Cooper in front of a horde of astonished guests attending the party. Wallis had left Warner Brothers a while before to take up residence at Paramount as an independent, and although this was not one of his best productions, it still is remembered fondly by devotees of Cooper and Bergman. Robson gained an Oscar nomination as Best Supporting Actress, the film's only nomination.