It is 1917. Daisy Heath (Sullavan) is a hard-drinking, hard-partying, hard-living actress and performer on the New York stage, headliner of a Broadway musical revue. She is in what appears to be a sort of casual sex relationship with Sam Bailey (Pidgeon), the boss of the revue. The United States has just entered World War I, but with all the wild parties she goes to and all the hangovers she has afterwards, Daisy hardly notices.
Also in New York is Bill Pettigrew (Stewart), a country boy from Texas who joined the army at the outbreak of war and is undergoing basic training in a camp outside the city. After Daisy's chauffeur nearly runs Bill over in the street, an irate traffic cop orders her to give Bill a ride back to the army base. Bill's buddies back at the base are boggled when he is dropped off by a gorgeous actress riding in a fancy car. Bill starts telling lies about how she's his childhood sweetheart, which leads his buddies to demand he back his stories up, which leads to Bill shamefacedly approaching Daisy and asking her to pretend to be his sweetheart—and sure enough, sparks start to fly between them. Sparks which Sam Bailey, who is witty and urbane and the polar opposite of guileless hick Bill, does not like at all.
- Amusement Park: Bill takes Daisy to Coney Island, and naturally, Daisy the jaded party girl has a grand time.
- Anguished Declaration of Love: Bill, who's gone AWOL to see Daisy as his troop transport is leaving in a matter of hours, finally spits it out as they are dancing. They hurriedly get married before he leaves, even though Daisy's figured out by now that she really loves Sam.
- Blatant Lies: Bill, basking in the admiration after Daisy drops him off at the camp, starts telling tall tales about how she's his long-time sweetheart. The other soldiers call his bluff and demand to meet Daisy, and, much to Bill's relief, she plays along.
- Could Say It, But...: The messenger who brings orders to Bill's camp, and then tells the extremely curious soldiers "I ain't saying anything...but if any of you guys get seasick, you'd better not eat a full meal." They are shipping out to France that night.
- Country Mouse: Bill the rube from Texas, who stares at the skyscrapers and twice nearly gets flattened by traffic because he's just not used to so much of it. He notes how much more expensive stuff in New York is.
- Downer Ending: Yup, Bill is killed in France, leaving Daisy to weep as she powers through a performance of "Pack up Your Troubles in Your Old Kit Bag" at a nightclub.
- Establishing Character Moment: We get a good handle on what Bill is like the instant we see him, when he's craning his neck and gawking at the skyscrapers as his unit marches through Manhattan.
- Hangover Sensitivity: On two different occasions Daisy wakes up in distress after late night parties.
- Have a Gay Old Time: "When you've a lucifer to light your fag," a lyric from WWI marching song "Pack up Your Troubles in Your Old Kit Bag", sung twice in the movie.
- Love Triangle: Daisy, Bill, and Sam. The presence of eager, adoring suitor Bill causes Sam to realize just how deep his feelings for Daisy are.
- Mammy: Hattie McDaniel plays her usual sassy maid.
- Match Cut: From the legs of Bill and his fellow soldiers marching in formation down New York's streets, to the legs of the chorus girls in Daisy's show, kicking.
- Really Gets Around: Sally the waitress at the drug store, who promises three different soldiers that she'll wait for them, much to Bill's amazement.
- Romantic False Lead: Bill, suprisingly enough, since he's played by James Stewart. While Daisy clearly develops feelings for Bill she realizes that she truly loves Sam. However, she marries Bill anyway, because she feels she owes it to him and she doesn't want to break his heart.
- Romantic Rain: Lampshaded. Daisy says it's about to rain and then muses about how in New York, the rain always waits for the right moment. Then when it finally starts to rain as Bill is making his Anguished Declaration of Love, Daisy says "I told you it always rains at the right time!"
- Spinning Paper: The opening scene is a Spinning Paper montage of newspapers dated April 6, 1917, announcing America's declaration of war on Germany.