Clara Spencer’s husband takes her to the bus station so that she can depart for New York, where she will be treated by a proper dentist for her chronic toothache. Clara, armed with her pain medication, takes the redeye bus to the city. On the bus, Clara immediately falls asleep and only awakens when the bus halts for a short break.
She enters the store and sits down, quickly falling asleep again. She awakens when a man in a blue suit starts talking to her about his travels to a distant land. Back on the bus, the man, Jim, continues to talk to her, though Clara is only dimly aware of him, so groggy is she. The bus stops again, jerking her awake, and Clara finds herself at the previous restaurant, following Jim into it before separating to go to the restroom.
Jim waits for Clara in the restaurant, and they return to the bus. Upon arriving at New York, Jim says goodbye to Clara after escorting her off the bus. She falls asleep at the New York station again, but someone awakens her before seven o’clock in the morning. As Clara gets on the escalator, she notices Jim following her again, and he continues to talk about his travels. As she stands on the street corner, Jim comes towards her, then leaves, after handing her pearls.
Clara falls asleep at the restaurant where she eats breakfast, but she does eventually make it to the dentist. The nurse lets her into the dentist immediately, who refers her to an oral surgeon to have her left molar removed. Clara feels that her identity is narrowed down only to her tooth, given the extreme attention given to and the pain caused by her tooth.
Clara takes a taxi to the oral surgeon, where the receptionist is slightly less friendly. Another nurse leads her to the dentist, and Clara is nervous and asks if the procedure will hurt. She receives an anesthetic during the operation, which makes her even more confused, and Clara dreams of Jim. When she awakens, the nurses send her on her way, with instructions not to wash her mouth so that the blood can clot.
Clara stops in the washroom, where some other women are preparing to go out for lunch. Clara washes her face, but when she looks into the washroom mirror, she cannot identify herself among the reflections of the other women. The other women leave, and Clara struggles with her identity. She notes that her barrette says “Clara,” but she throws it away in the trashcan. She checks her wallet, refreshes her makeup, and throws away a pin with her first initial.
Unhappy with her reflection, Clara wonders how old she is and retouches her makeup so that she is not as pale. She has no recollection of who she is, where she is from, or how to return home to her husband. She purposefully leaves the building, and when she returns to the streets below, Jim appears and takes her with him. Clara does not notice the odd glances sent her way by passersby, and she believes that she is running through hot sand with Jim at her side.
As in previous stories, Jim Harris's presence in "The Tooth" indicates Clara's growing mental instability. At the beginning of the story, as in "The Daemon Lover," Jim Harris could potentially be a real character. He is first mentioned as a man Clara encounters on her bus trip to New York. He stops to talk to her at one of the bus's restaurant stops, then sits next to her on the bus. Then, after Clara arrives in New York, she continues to encounter him randomly—at the train station and on the street. As the protagonist grows more disoriented, Harris's actions also become more bizarre. For example, he shows Clara a handful of pearls as she waits for a streetlight to change so that she can cross the street. Finally, when Clara imagines herself to be running on a beach with him—even though she is actually still in New York—the reader realizes the full extent of her madness.
Harris disappears briefly in the second section of the story, while Clara is attended by various nurses and dentists. Here, she believes that her individuality as a person has been superseded by the attention paid solely to her toothache. "Her tooth ... seemed now the only part of her to have any identity" (199). This feeling suggests the disintegration of her identity and her perception of reality. She loses touch with herself, with her grip on her own identity, and thus loses her grip on reality.
After her operation, Clara can no longer recognize herself, not even her own physical appearance. The climax of the story occurs in the women's bathroom after her oral surgery. Clara realizes that she is wholly unable to distinguish herself from the other women in the bathroom: "She looked into the mirror as though into a group of strangers, all staring at her or around her; no one was familiar in the group, no one smiled at her or looked at her without recognition; you'd think my own face would know me" (204). But after examining her belongings and monogrammed barrette, Clara chooses to discard these items. She has no recognizable identity and gets rid of any vestiges of it. Having done so, Clara sees Jim for a final time. She believes herself to be running away with him on a distant beach. As in "Trial by Combat," Clara's barrette and pin, like Emily Johnson's initial pan, are concrete symbols of her sense of self. Her act of throwing them away serves as a metaphor for her loss of identity.
Clara's relatively fast (one day) transformation and loss of self are a more obvious manifestation of what happens more subtly in other Jackson characters who are oppressed by their lifestyles and environments. Like Margaret of "Pillar of Salt," Clara finally self-destructs in New York City. The abrupt transition from suburban to urban life destroys her, much like it does Margaret. She loses all notion of who she is, where she lives, and so on. The story concludes with Clara running through the streets of New York barefoot, though she believes herself to be on a beach with Jim Harris. (Maybe it is the medication, but she has been unstable from the beginning.)
The conflict of this story takes place within Clara's self and her struggle to maintain her conscious realization of her identity. James Harris is not necessarily a direct antagonist; as in "The Daemon Lover," his presence corresponds to the presence of mental illness or instability, perhaps of evil and malice. He is not the source of Clara's insanity but a manifestation of her growing madness.
Throughout most of the story, Jackson infuses the narration with blurriness. The tone of the story is muddled, drifting without clarity between Clara's real experiences with the outer world and her inner fantasies of Harris. The story commences with Clara's husband dropping her off at the bus station to leave for New York—this most likely is real. Then, she supposedly meets Harris: "He was wearing a blue suit and he looked tall; she could not focus her eyes to see any more" (196). His existence again is questionable, for he does not interact with anyone but Clara. Jackson does not distinguish explicitly between Clara's reality and fantasy lives. Harris's descriptions occur when Clara is groggy from sleep and medication.
Only at the end of the story, when Clara has wholly lost herself, does she appear to act with conscious conviction and deliberation, no longer disoriented from lack of sleep or from medication. Finally, the reader determines that Clara is out of touch with reality. She is "oblivious of the people who stepped sharply along the sidewalk,” and “not noticing their occasional curious glances, her hand in Jim's and her hair down on her shoulders, she ran barefoot through hot sand" (207). By including the witnesses' "occasional curious glances," Jackson makes clear to the reader that Clara is behaving abnormally with reference to reality (probably not just because her face is puffy or pale from the surgery). Thus, the distinction between Clara's fantasy and reality is finally made clear at the end of "The Tooth," thus demonstrating with certainty that she has gone mad.