Sometimes in April

Augustin, a captain in the Rwandan Armed Forces, lives in Kigali with his wife Jeanne, a Tutsi hospital worker with whom they have two sons, Yves-André and Marcus, and a daughter, Anne-Marie, who is staying in an all-girls Catholic boarding school 150 kilometres from Kigali. Despite constant political disagreement, he remains in close contact with Honoré, a pro-Hutu Power radio personality working for Radio Télévision Libre des Mille Collines (RTLM). Augustin is also friends with Xavier Muyango, a fellow Hutu officer and fiancé to Felicie, a Tutsi.

By April 1994, the power-sharing agreement between the Hutu-dominated Rwandan government and Paul Kagame's Tutsi-led Rwandan Patriotic Front (RPF) is breaking down as President Juvénal Habyarimana is viewed by Hutus to be conceding too far in favor of the Tutsis. Despite history of anti-Tutsi violence by hardline Hutus earlier in the Rwandan Civil War and warnings from Honoré and the Hutu ranks in the government that violent action from Hutu extremists may recur, Augustin insists on taking the position of a moderate and remaining in the country to Jeanne's disapproval. On the night of April 6, Habyarimana is killed when his plane is shot down and Prime Minister Agathe Uwilingiyimana is assassinated by government soldiers the following morning, reigniting the civil war and signaling the start of mass killings of Tutsis and moderate Hutus by génocidaires comprising pro-Hutu government soldiers and militiamen backed by Hutu extremists, who were prior civilians, indoctrinated by Hutu Power propaganda.

In response to the outbreak of violence, Xavier and Felicie seek refuge at Augustin's home. Fearing danger to his family, Augustin calls on Honoré to use his influence in the community to safely transport his family and Felicie to the Hôtel des Mille Collines, which is harboring refugees, while confident that Anne-Marie is out of harm's way. As Augustin learns from Honoré that he is documented as a Tutsi sympathizer by the government, he elects to stay at home alongside Xavier until it is safe to head to the hotel. On route, Honoré manages to slip his passengers through génocidaire roadblocks, but is stopped at an unexpected military checkpoint, where the group is detained and a scuffle ensues.

After a few days of hiding, Augustin and Xavier escape the house and trail a UNAMIR convoy evacuating expatriates, but are separated from the convoy at a militia roadblock when the officer in charge of the convoy refuses to help. Augustin's life is spared but Xavier is executed as he has been branded a traitor on the radio. Augustin eventually reaches the hotel but is unable to locate his family, and remains there for the rest of the genocide. Meanwhile, Jeanne awakens in shock without her sons at the Sainte-Famille Church over a week after the altercation at the checkpoint. Felicie is later seen lined up for execution by the church building.

Génocidaires eventually breach the school Anne-Marie resides at to screen for Tutsi elements, confronting Martine, a teacher at the school sheltering a group of students, including Anne-Marie, in a dormitory. The students rally behind Martine in solidarity as Martine refuses to divide them into Hutus and Tutsis, only for the group to be indiscriminately slaughtered by gunfire from government soldiers. Martine and Victorine, a fellow student, survive and find Anne-Marie alive but mortally wounded; as they escape, Anne-Marie eventually dies. The two soon find safety among the thick vegetation of the Kayumba swamps, where they are rescued by advancing RPF soldiers.

Towards late-July, the RPF has scored massive territorial gains while members of the Hutu political and military elite and Hutu civilians flee the country out of fear of reprisal from the RPF, ending the civil war and the genocide. Augustin seeks out Anne-Marie at her school, only to find Martine and another woman tending to bodies in the dormitory where the massacre occurred. He grieves when Martine confirms that Anne-Marie is dead.

Haunted by the events in 1994 and resigning to never learn of what had become of Jeanne and his sons, Augustin finds work as a school teacher and lives unmarried with Martine, who remains traumatized by her experience at her old school. Around the tenth anniversary of the start of the genocide, Augustin receives a letter from Honoré expressing interest to discuss in person the fates of Jeanne and his first sons. Honoré has been detained in Arusha in Tanzania, where he is tried by the International Criminal Tribunal for Rwanda for his role at RTLM, after being on the run until his arrest in Italy in 1997.

On Martine's insistence, Augustin reluctantly flies to Tanzania to attend the trial hearings as a visitor, dithering to meet Honoré. Furious to learn that those charged for inciting the genocide live in relative luxury with ample medication and meals while regular Rwandans struggle to survive, Augustin doubts remaining in Tanzania. His stance softens when he befriends Valentine, another genocide survivor. She invites him to listen to her testify in court as an anonymous witness, where he hears of the constant rape she endured in the hands of Interahamwe militiamen while as a mother of a baby. Augustin eventually learns that Valentine is caring for two young sons.

Inspired by Valentine's courage to testify, Augustin is motivated to meet Honoré. At the meeting, Honoré recounts the events that unfolded at the checkpoint to the hotel in 1994: The soldiers were ordered to kill Jeanne, Yves-André and Marcus due to their Tutsi lineage. Augustin's sons were promptly shot dead, but in their excitement, the soldiers presumed Jeanne was also dead despite only being knocked unconscious by a rifle butt. Honoré hid Jeanne in a ditch, before carrying her to the safety of the church at night. For objecting to the kill order, Honoré was listed as a traitor and lost his privilege for safety, forcing him into exile and being unable to aid Jeanne any further. Honoré would later learn that while Jeanne was initially safe and pleaded to join Augustin at the hotel, she was raped by soldiers after the military began to probe the church for Tutsis. With the imminent threat of being killed, Jeanne sacrificed herself with a grenade to save a few rape victims and inflict injury on her aggressors.

Reflecting on Honoré's revelation, Augustin finally finds peace and returns to Rwanda to raise his new family with Martine, who is now expecting a son. The film closes with Martine reconciling with her past by laying flowers at the remains of the school dormitory before attending a nearby Gacaca court to recount her experiences in the genocide.