There are several points in Passing where Irene reflects on the threat to her marriage posed by Brian's discontent with their life and his desire to move to Brazil. To illustrate the seriousness of this threat, Larsen uses a metaphor equating Brian's dissatisfaction with a fire that Irene must suppress:
[I]n her there was no slackening of the agitation, of the alarms, which Brian’s expression of discontent had raised [...] Yes, it would die, as long ago she had made up her mind that it should. But in the meantime, while it was still living and still had the power to flare up and alarm her, it would have to be banked, smothered, and something offered in its stead.
The fire of Brian's constant dissatisfaction is a blaze that Irene feels compelled to extinguish whenever she sees it flickering. She perceives his unrest as a dangerous conflagration that could consume their marriage if left unchecked. The author’s use of words like "banked" and "smothered" highlight Irene's determination to control and subjugate Brian. This use of fire as a metaphor does more than illustrate the heat and intensity of Brian's suppressed desires, however. It also underscores the potential destructiveness to Irene if those desires are not eventually addressed. Irene believes that by suppressing this metaphorical fire, she can maintain the stability of their relationship and her security at home. Any disruption to the life they have established cannot be allowed. Whenever she is concerned Brian is starting to yearn for Brazil, her "alarms" begin to go off.
Irene watches Clare as she sees her across the room at a party she throws, talking to Brian. She uses the metaphor of a mask as she observes Clare’s carefully unmoving expression and Brian's responses:
Clare’s ivory face was what it always was, beautiful and caressing. Or maybe today a little masked. Unrevealing. Unaltered and undisturbed by any emotion within or without. Brian’s seemed to Irene to be pitiably bare. Or was it too as it always was? That half-effaced seeking look, did he always have that? Queer, that now she didn’t know, couldn’t recall.
The metaphor of Clare's face being "masked" suggests she is hiding her true emotions behind a façade that appears "beautiful and caressing." It isn’t her facial expressions that “caress” people, but her face itself; her beauty is still inviting even if she looks impassive. Larsen’s use of the word “ivory” gives the reader the sense that Clare's face is hard, white, and unyielding. As is typical for Clare, however, these descriptions are inherently contradictory; she is both “caressing” and “ivory” at once. This “mask” creates a sense of uncertainty for Irene, who can see that Clare is concealing something before they have even spoken.
In contrast to Clare’s “mask,” Brian's face is “pitiably bare.” This disdainful observation by Irene indicates that she thinks he’s shamefully exposing how he feels in comparison to "masked," sophisticated Clare. However, because she fears she’s losing control of him, Irene questions whether this "half-effaced" exposure is genuine, or if her own perceptions are clouded. She’s confused by her own need to observe and control people. She can’t remember if Brian's face has always held this "half-effaced seeking look" and can only surmise that Clare’s face is “maybe a little masked.”
Irene senses a change in Brian's demeanor that fills her with anxiety that he’s being unfaithful to her. Larsen uses a metaphor to illustrate this uncomfortable realization:
It was the knowledge that, for all her watching, all her patient study, the reason for his humour still eluded her which filled her with foreboding dread. That guarded reserve of his seemed to her unjust, inconsiderate, and alarming. It was as if he had stepped out beyond her reach into some section, strange and walled, where she could not get at him.
Larsen employs metaphor here to depict the emotional distance growing between Irene and Brian. The "section, strange and walled" that Irene has begun to notice is a a secret part of Brian's mind that is inaccessible to Irene. A lot of her personal feelings of safety and security arise from her certainty that she can control Brian and predict how he’ll react to things. This metaphor shows Irene's frustration and fear as she realizes there are aspects of Brian she cannot understand or reach; soon after this, she has a similar realization about Clare’s hidden depths. It’s as if his new secrecy is itself a betrayal or an insult to her, “unjust, inconsiderate, and alarming.” Although he’s still there, he has also crossed a threshold that she cannot "pass" over.
Irene is startled and reacts instinctively when she runs into Clare's husband, Jack, while walking with Felise in Harlem. The author uses a metaphor to depict Irene's snap decision to double down when Jack recognizes her as a Black woman:
Instinctively, in the first glance of recognition, her face had become a mask. Now she turned on him a totally uncomprehending look, a bit questioning.
Instead of trying to explain herself to Jack and protect her own ability to "pass," Irene pretends not to recognize him. It’s as though the version of herself that she was when she met him—the "passing" as white version—is totally separate from her identity here as a Black woman in Harlem. The metaphor of the "mask" that Larsen uses here illustrates Irene's swift and total transformation. Her face, which was normal when she was speaking with Felise, becomes a mask "at the first glance of recognition" in order to conceal her true emotions and identity.
By describing her face as a mask, Larsen is describing this protective façade Irene dons. It serves a dual purpose: it shields her from any potential public hostility from Jack and allows her to pretend she’s never met him despite them both knowing she has. The "uncomprehending look" she gives him reinforces this act, presenting a version of herself that is safe and inaccessible. The mask metaphor also signifies the disconnect between the "passing" Irene who knows Jack and the unknown Black woman she must pretend to be in that moment. She cannot be both at once, so she must snap the "mask" on in order to face Jack.
In this passage, Nella Larsen uses metaphor to illustrate Irene's newfound sense of identity and determination. Irene thinks about her future after realizing that Clare and Brian are definitely sleeping together, and she comes to a decision that she’ll say nothing. She uses a metaphor that aligns her with a growing plant to drive this message home:
Now that she had relieved herself of what was almost like a guilty knowledge, admitted that which by some sixth sense she had long known, she could again reach out for plans [...] She belonged in this land of rising towers. She was an American. She grew from this soil, and she would not be uprooted.
The metaphor of Irene as a plant that "grew from this soil" refers to her deep roots in Harlem and in her marriage. By likening herself to a plant firmly embedded in the "land of rising towers," she asserts her unshakable connection to the city she has chosen as her home and the man she has chosen to build that home with. Rather than making her want to give up and run away, admitting that Brian is having an affair makes her double down on her attempts to stay stable and "reach out for plans" to control his actions. The notion of "not be[ing] uprooted" reflects her determination to hold on to her life and identity despite Clare’s attempts to disrupt her.
Interestingly, in this passage Irene identifies herself simply as "an American," shifting her identity from being based in race or gender to a broader national affinity. In the face of betrayal she finds this comforting. This perspective allows her to see beyond the discomfort of the pain she feels and reassert control over her life. Despite anything Brian and Clare might do, she thinks, she has every right to stay where she is. She is in America, and she is an American who will not “be uprooted.”