We begin at the ceremony for the prestigious Sarah Siddons Award, an award for accomplishment in the theater. An old man talks about acting and the theatre and…wake us when this guy is done. This is more boring than watching all four hours of the Academy Awards.
Oh, good, a voiceover: Addison DeWitt, smarmy theater critic (redundant?), interrupts Methuselah to introduce us to all the major characters:
Let's find out all about Eve, shall we?
Just as Eve reaches for her award, the screen is paused in freeze frame and we flash back… not all the way back to Adam, but a few months to when everyone first met Eve.
Eve is Margo's biggest fan. She sees every performance of her Broadway play, Aged in Wood. After Karen introduces Eve to Margo, everyone loves Eve. Margo hires her as her assistant, and before she knows it, Eve has wormed her way into Margo's life.
The tipping point is when Eve schedules a phone call (using a real-life telephone operator, the Siri of the 1950s) to Margo's boyfriend, Bill, without her knowledge and sends Bill a telegram herself.
Is that scheming hussy threatening to take Margo's man?
Margo thinks so, but everyone else thinks Margo's just crazy jealous. See, ancient, grizzled old Margo (she's forty) is insecure about her age and what it means for her career, and her friends think she's taking her frustration out on Eve. At Bill's welcome home party, Margo warns everyone, "Buckle your seat belts. It's going to be a bumpy night." Margo gets drunk, treats her pals like garbage, and makes everyone mad at her.
In the aftermath, sweet, young, innocent Eve (she still has everyone tricked) finagles her way into the theater as Margo's understudy. Margo is furious, having an argument with Lloyd and Billin so nasty that Bill leaves her. Karen wants to teach Margo a lesson about humility, so she finds a way for Eve to perform as the lead in the play for one night. Coincidentally (read: totally on purpose due to Eve's conniving plans) all of New York's critics are at Eve's bravura performance, writing rave reviews.
Eve teams up with Addison, who writes a scathing article about crusty old Margo being too old and crusty to be on stage. Bill returns to Margo to comfort her, and she decides to quit acting and marry him. The movie acts like this is a good thing. With Margo out of the picture, Eve has free rein. She tries to seduce Bill, and fails, so she tries to steal Lloyd from Karen, and fails. Despite clearly being a manipulative crazy person, she is awarded the lead in Lloyd's next play.
Before the play opens, Addison exposes all of Eve's lies.
Eve throws a fit that Addison called her out on all her deception, and she refuses to act that night. Addison orders her to perform, and to do her best. He's in control of her now.
Voilà—we're back at the beginning of the movie as Eve, unfrozen, receives her Sarah Siddons Award for being Broadway's best actress. Her former friends glower in the audience, completely disgusted and unimpressed. After receiving her award, Eve returns to her hotel room, where a strange girl is lurking. The girl introduces herself as Phoebe, the president of the Eve Harrington Fan Club. Eve lets the girl stay, and implies that the girl can come with her to Hollywood.
Addison arrives at Eve's room with her award, which she left in the cab. He gives the award to Phoebe, who secretly puts on Eve's award ceremony cloak and stares at herself in the mirror, pretending the award is hers.
Looks like we have another Eve on our hands...