On her birthday night in Los Angeles, Norah Larkin opens a letter from her fiancé, a soldier serving in the Korean War, and discovers that he plans to marry someone he met in Tokyo. The revelation hits hard, leaving Norah reeling as she processes a future that isn’t what she hoped for.
Devastated, she dials up a date with Harry Prebble, a calendar-girl artist who hosts a South Seas–themed hangout. When she arrives at the Blue Gardenia, Prebble is surprised to find Norah waiting instead of her roommate Crystal Carpenter. He tends to her with tropical cocktails, and Norah’s confusion and sadness deepen into drunkenness as the evening unfolds.
Back at his apartment, Prebble tries to push the evening into a predatory direction as he proclaims his art. Norah resists, and a terrifying struggle ensues: she fights him off, hitting him with a fire poker and shattering a mirror before fleeing, leaving behind her suede pumps as a telltale trace of what happened.
The next morning, Norah is awakened by Crystal and realizes she cannot remember the previous night in full. Meanwhile, police at a crime scene question Harry’s maid, who confesses to cleaning the poker and moving the shoes, thereby ruining the scene’s physical evidence.
At the telephone office, investigators press the women who posed for Prebble’s drawings. As Norah uncovers why the investigation has spiraled, she hunts for a newspaper account of the slaying and begins to dredge up a fragmentary memory linked to a specific song playing on a record. The case gains a public face when popular columnist Casey Mayo dubs the presumed killer the “Blue Gardenia murderess.”
That night, Norah’s roommate Sally Ellis reads aloud the account that the suspect wore a ta ffeta dress. Terrified, Norah hides her own dress by wrapping it in a newspaper and slipping out in the early hours to burn it in an outdoor incinerator. A passing patrolman stops her for burning after hours, but lets her go with a warning.
To capitalize on the sensationalism, Mayo writes a column urging Norah to surrender to him rather than the police, promising fair treatment if she cooperates. He receives several bogus calls, but one genuine one convinces him to meet what he believes is a friend. They talk at a diner, where Norah supplies a version of events that includes the detail of Prebble playing the Nat King Cole recording of “Blue Gardenia” on the phonograph, a detail Mayo confirms by selecting the same music from a table-side jukebox. Mayo agrees to meet Norah’s supposed friend the next day. Norah returns home and confesses to Crystal, who offers sympathy.
The following day at the diner, Crystal directs Mayo to Norah’s booth, and Mayo is struck by how his feelings have shifted; he realizes he’s begun to fall in love with her. The moment is interrupted when the police arrive on a tip from the counterman and arrest Norah. She leaves town, convinced that Mayo has betrayed her, while Mayo’s concern lingers about his own motives and loyalties.
Chasing a new lead, Mayo and Police Captain Sam Haynes follow the trail to a local music shop. The clerk reveals that Harry’s ex-girlfriend, Rose Miller, sold him the record, and the authorities call Rose, who locks herself in a restroom and attempts suicide as officers close in.
From a hospital bed, Rose confesses her side of the story: after Norah passed out, Rose visited Harry’s apartment distraught—and possibly pregnant—demanding that he marry her. He refused and instead started playing the Tristan und Isolde record that had drawn them together. Rose notices Norah’s handkerchief near the record player in the room, and in a fit of jealousy she bludgeons Harry with the poker.
With the complicating truth in hand, Norah is cleared and freed. She forgives Casey and makes her feelings known, realizing she wants him. In a final, wary gesture, Casey tosses his “little black book” to his friend Al, signaling a new, unsettled path beyond the case and its shadows.
