The following version of this book was used to create this study guide: Diop, David. Farrar, Straus and Giroux, 2020.

At Night All Blood Is Black takes place in the trenches of the French army during World War I. Diop also take readers to the Rear, a hospital set up for soldiers traumatized by war, and down memory lane to the small village of Gandiol in Africa, where Alfa, the protagonist, grew up and met his best friend, Mademba. It is narrated in the first person and follows the perspective of Alfa and, at the end of the novel, Mademba, both of whom grew up in Gandiol and signed up to defend France in the war. It is about Mademba's tragic and ugly death on the battlefield and how Alfa attempts to avenge, overcome, and eventually transcend the tragedy of that death.

Section 1 of the novel opens with the death of Mademba, Alfa's childhood best friend. His stomach is sliced open and his guts are spilling out of his body. As he writhes in pain, he begs Alfa to slit his throat to end the agony, but Alfa falters out of respect for human law. Mademba dies a slow, painful, undignified death, and when he has finally passed, Alfa carries his body back to the trench and receives a Croix du Guerre for his courage. Traumatized by what he has seen, Alfa begins a macabre ritual of seeking out German soldiers, slicing open their stomachs, and slitting their throats, in an effort to both avenge Mademba and reenact what should have been the last scene of his life. He then severs their hands and brings them back to his trench.

Section 2 follows Alfa as he mutilates these German soldiers. Eventually his trench-mates resent his obsession with death and mutilation, and rumors spread that Alfa is a soldier sorcerer. Jean Baptiste is an exception to this rule; he enjoys playing with the severed hands that Alfa brings back and mocking the Germans. He pays the price for this when the Germans, sick of being mocked with the hands of their dead comrades, shoot his head off.

Section 3 opens with Alfa avenging the death of Jean-Baptiste and the rest of the soldiers coming to resent the war itself, not simply Alfa. When they refuse to obey Captain Armand's whistle, he ties their hands behind their backs and forces them to rush out of the trenches and into the battlefield, defenseless against the shots of the Germans. He also commands Alfa and his trench-mates to kill those soldiers who refuse to obey him. After this hypocrisy and ugliness, Alfa is commanded to go to the Rear because his way of waging war - mutilating German soldiers - is outside regulation. In the rear, Alfa softens up and begins to reminisce about his first love, Fary Thiam.

Section 4 features Alfa's drawings, assignments given to him by Doctor Francois in an attempt to heal his trauma and wash his mind from the filth of war. Alfa draws a picture of his mother and takes a trip down memory lane, recalling her love, her beauty, and her eventual departure. He then draws a picture of Mademba and takes another trip down memory lane, recalling Mademba's love and support for him when he lost his mother. This section shows readers Alfa's past and develops his character more fully.

Section 5 reveals Alfa entirely healed of his past, burying the seven hands and deciding to have sex with Mademoiselle Francois, the doctor's daughter. At the moment of climax, Alfa gives his body to Mademba from beyond the grave, and Mademba comes back to life in the middle of sex, losing his virginity to a woman he does not know in a body that is not his own. By the end of the novel, it is clear that both Alfa and Mademba live within Alfa's body, fusing themselves together to create a new man with a new life.