Nella Larsen’s Passing opens with the protagonist Irene reading the second letter she has ever received from her childhood acquaintance Clare, in which Clare asks Irene if they can see each other. The letter angers Irene, though the reason why is not yet clear.
The narrative then flashes back to two years before, when Irene is shopping for souvenirs for her sons in the sweltering heat. Irene, who lives in Harlem, is visiting her father in Chicago, where Irene grew up. Irene is about to faint when a friendly driver helps her into his car and offers to drive her to the Drayton, a white hotel, so that she can buy an iced tea. Though Irene is black and lives in a black community, she is light-skinned enough that she can pass for white when she is alone. Irene accepts, and the man drops her off at the hotel.
Irene is at the hotel drinking iced tea when a couple comes into the bar and sits down. Irene watches the pair, gazing at the beautiful and seemingly white woman. The man leaves, but the woman stays at her seat at a table near Irene’s and Irene realizes that the woman is staring at her. Irene worries that the woman realizes that she is black. However, after a few moments, the woman comes over to Irene, and Irene realizes that she is Clare Kendry, a childhood acquaintance who left their Chicago neighborhood after her father’s death. During Irene’s adolescence, Clare was the subject of many rumors that she had passed into white society and was living as a white woman entirely. Irene and Clare chat, and Irene tells Clare about her life. Irene finds out that Clare is married to a white man, and that her husband does not know she is black. Irene gets up to leave and Clare insists that Irene visit her before Irene returns to New York.
The next Tuesday, Irene, albeit hesitantly, goes to Clare’s house for tea. At Clare’s, Irene finds that she is not the only guest—Clare and Irene’s childhood acquaintance Gertrude is also present. Like Clare, Gertrude married a white man, but unlike Clare’s husband, Gertrude’s husband is aware of her racial background. The women insensitively discuss race and skin-color, leaving Irene, who is married to a black man and lives in a black community, angry and hurt. Eventually, Clare’s husband John returns home. John, who does not know any of the women are black, including his own wife, immediately begins spewing racial slurs and making racist statements. Irene is irate, but she laughs uncontrollably at the irony of the situation. As soon as Irene can politely leave, she does so. Afterward, Clare sends Irene a letter thanking her for her visit, and Irene, furious does not respond.
The narrative flashes forward again to the moment in the opening scene when Irene is reading the second letter Clare has sent her, two years later. In the time since Irene last saw Clare, her own marriage with Brian, who is bitter that Irene will not move with him to South America, has become strained and distant. Irene resolves not to answer the letter, not wanting to see Clare after their last encounter. However, Clare shows up at Irene’s house in New York and asks why Irene did not answer her letter. Irene tells Clare that she and Brian have decided that they cannot associate with Clare because if John were to find out it would put them all in danger. Clare cries and begs to be invited to the Negro Welfare League dance that Irene is helping to host. She talks about how hard it is facing John’s daily racism. Finally, Irene concedes to let Clare come. Irene has mixed feelings of annoyance, jealousy, and admiration towards Clare, who she thinks is selfish but beautiful.
At the dance, Irene talks with her friend Hugh Wentworth about passing, race, and beauty. Clare wins over Irene’s social circle with her charm and good looks. Even Brian, who did not want Irene to associate with Clare, warms up to her. Following the dance, Clare becomes Irene’s friend and a fixture in the Redfield household. Despite this newfound friendship, Irene continues to harbor muddled feelings of attraction, jealousy, and resentment towards Clare. Meanwhile, Irene’s marriage with Brian becomes more and more tense. They fight over how to best raise their two boys, Ted and Junior, and Brian’s feelings of restlessness. Irene becomes anxious and depressed. Clare, Irene, and Brian frequently attend social events together, and sometimes, when Irene is sick, Clare and Brian go alone.
One day, Irene is hosting a tea party for Hugh. She is napping before the party when Brian comes to wake her up and tell her it is time to get ready. Brian informs Irene that Clare is already downstairs. Irene is confused, because she did not invite Clare. Brian finally sheepishly admits that he invited her. Irene suddenly feels suspicious that Brian and Clare are having an affair. Through the tea party and the next several weeks, Irene’s suspicion mounts until finally Irene is convinced that Brian is cheating on her. Still, Irene is determined to preserve her marriage. Irene fantasizes about ways she could rid herself of Clare, imagining what might happen if Clare’s daughter Margery died or John found out about her black ancestry. Irene decides that Clare and John cannot get divorced, because otherwise Clare will be free to pursue Brian. Whenever Clare expresses the desire to be free of John and return to the black community permanently, Irene tries to remind her of her obligations to her daughter.
One day, during an afternoon out with her friend Felise, Irene runs into John on the street. John recognizes Irene from their meeting in Chicago and says hello, but when he sees Felise, John realizes that they are both black. Irene, realizing how dangerous this could be for Clare, pretends not to know John. Afterward, Irene understands that, because John now knows she is black, John might become suspicious of Clare. Irene thinks she should warn Clare or tell Brian about the encounter, but instead she says nothing.
Irene, Clare, and Brian go to a party at Felise and Dave Freeland’s sixth floor apartment. At the party, Irene is melancholy and sullen. She opens a window to let in fresh air. There is a knock on the door and when Felise opens it, John bursts into the room, demanding to know where Clare is. Clare backs away from him towards the window. John yells racial slurs, and the room is tense. Irene, in a panic, moves toward Clare and touches her on the arm. Irene is unclear what happens next, but the next thing she knows Clare has fallen out the open window. Everyone rushes downstairs to see what has happened, but Irene is dazed and stays upstairs for a few extra minutes. Finally she goes downstairs and learns that Clare is dead. She starts to cry and then faints. It is never made clear if Irene pushed Clare through the window, Clare committed suicide, or she fell by accident.