The following version of this novel was used to create the guide: Akbar, Kaveh. Martyr!. Alfred A. Knopf, 2024.

As Martyr! begins, an Iranian-American man named Cyrus Shams finds himself occupying a strange role at a small college in Indiana, Keady University; he works as a paid actor in the university's hospital lab, where he embodies various terminally ill patients in order to train nursing and medical students on their bedside manner. Cyrus lives with his roommate and best friend, Zee, and has struggled for much of his adult life with substance abuse and addiction, habits that began following his mother Roya's tragic death at the hands of the U.S. military and his father Ali's passing after years of grueling work at a chicken farm. Cyrus meets with his sponsor, Gabe, who chastises Cyrus for refusing to abandon his fascination with his Iranian heritage and his family's history of grief, both of which Gabe feels hold Cyrus back from making a full recovery. Cyrus grows angry with Gabe after Gabe criticizes him for his newfound interest in martyrs and martyrdom, chalking Gabe's advice up to a rude misunderstanding born out of Gabe's western disregard for Cyrus' Persian heritage. Upon returning home, Cyrus employs a familiar strategy to combat his insomnia: he imagines long conversations between two characters, in this case the television character Lisa Simpson and Cyrus' own mother, Roya.

The day after his meeting with Gabe, Cyrus joins his friends Zee and Sad James at the Naples Café, where the three often meet to attend the open mics that regularly occur there. After Cyrus brings up the topic of martyrdom to Zee and Sad James, Sad James informs Cyrus that an artist named Orkideh is hosting a strange exhibit at the Brooklyn Museum in New York City where visitors are allowed to come and ask her questions while she slowly dies of a terminal illness. Although Cyrus is initially reluctant to go to New York, Zee offers to go with him and manages to successfully convince him that such a trip would be valuable for Cyrus' goal of writing a book about martyrdom. The pair arrive in New York, and Cyrus has his first meeting with Orkideh, who is also Iranian-American; Cyrus and Orkideh immediately strike up a bond, and Orkideh urges Cyrus to return the following day and speak with her further. While wandering New York, Cyrus and Zee grow increasingly reflective about their relationship with one another, as Zee recalls how he and Cyrus used to go to a man named Jude's house to fulfill Jude's sexual fantasies of having men perform house work for him, while Cyrus reflects on the night when he and Zee first met, after a bad date that Cyrus had with a Republican woman named Kathleen.

Cyrus and Zee begin sleeping together while in New York, a custom that is not unusual in their relationship; though they have never considered themselves a romantic item, they are often intimate with one another, even when they are ostensibly in other committed relationships. Cyrus returns to the Brooklyn Museum and has a long, fulfilling conversation with Orkideh, which seems to irritate the other people waiting in line to speak with the artist. The following day, Cyrus returns to Orkideh again, and Cyrus opens up to Orkideh about his struggle with addiction and his mother's death at the hands of the U.S. military, which shot down the commercial aircraft in which Roya was traveling. Orkideh reassures Cyrus about his creative goals, urges him not to make himself a martyr by reminding him that his friends would be upset if he died, and consoles him about his mother's death. Only after he leaves the museum does Cyrus realize that Orkideh knew the circumstances of Roya's death even though Cyrus never divulged the details to her.

After returning from the Brooklyn Museum, Cyrus begins frantically researching Orkideh's artistic record, and discovers that one of her paintings, titled "Dudusch" (Farsi for "brother"), depicts a man dressed as an angel riding on horseback through a battlefield of fallen soldiers. This image stirs Cyrus, who notes that it appears to depict his uncle, Arash, whose role in the Iranian military was to dress up as the angel Gabriel and wander the battlefield in order to bring solace to the fallen soldiers in the moments leading up to their deaths. That evening, after having sex, Cyrus and Zee get into an argument in which Zee calls martyrdom "pointless" and Cyrus implies that both his life and his friendship with Zee are essentially meaningless, which prompts Zee to angrily leave the hotel room. Unsure of where to turn, Cyrus calls Arash in Iran, who tells him a story about his old car, whose tape deck was stuck playing Allegri's "Miserere" on loop. The next morning, Cyrus walks to the Brooklyn Museum while listening to the "Miserere," but discovers upon arriving that Orkideh has died overnight.

Cyrus faints after learning of Orkideh's passing, and one of the museum's docents has to help Cyrus to his feet and console him. On his way out of the museum, Cyrus receives a call from Orkideh's wife and manager, Sang Linh, who informs Cyrus that she needs to have a conversation with him and that Orkideh was in fact Cyrus' mother, Roya. After meeting Cyrus in Prospect Park, Sang explains that Orkideh left Iran because she was involved in a love affair with her close female friend, Leila, and that in order to orchestrate Leila's escape from her abusive husband, Gilgamesh, Roya and Leila exchanged identities, meaning that it was not Roya but Leila who was killed in the plane shooting while carrying Roya's passport. Roya came to New York, adopted the name Orkideh, began painting, and had her career elevated upon meeting Sang in a gallery. After processing this information, Cyrus realizes that he is tired of queer people dying for love, and manages to get back in touch with Zee, whom he reunites with in the park while New York City abstractly dissolves into a beautiful apocalyptic event in the background.