T’Challa, king of Wakanda, dies of a disease that his sister, Shuri, believes could have been cured by the “heart-shaped herb”. Shuri was attempting to synthetically recreate the herb after it was destroyed by Killmonger.

One year later, Wakanda is under pressure from other nations to share their vibranium, with some parties attempting to steal it by force. Queen Ramonda implores Shuri to continue her research on the heart-shaped herb, hoping to create a new Black Panther that will defend Wakanda, but she refuses due to her belief that the Black Panther is a figure of the past. In the Atlantic Ocean, the CIA and U.S. Navy SEALs utilize a vibranium-detecting machine to locate a potential vibranium deposit underwater. The expedition is attacked and killed by a group of blue-skinned water-breathing superhumans led by Namor, with the CIA believing Wakanda to be responsible. Namor confronts Ramonda and Shuri, easily bypassing Wakanda’s advanced security. Blaming Wakanda for the vibranium race, he gives them an ultimatum: deliver to him the scientist responsible for the vibranium-detecting machine, or he will attack Wakanda.

Shuri and Okoye learn from CIA agent Everett K. Ross that the scientist in question is Riri Williams, a student at MIT, and arrive at the university to confront her. The group is pursued by the FBI and then Namor’s warriors, who defeat Okoye before taking Shuri and Williams underwater to meet Namor. Angered by Okoye’s failure to protect Shuri, Ramonda strips her of her title as general of the Dora Milaje and seeks out Nakia, who has been living in Haiti since the Blip.[N 2] Namor shows Shuri his vibranium-rich underwater kingdom of Talokan, which he has protected for centuries from discovery by the world. Bitter at the surface world for enslaving the Maya, Namor proposes an alliance with Wakanda against the rest of the world but threatens to destroy Wakanda first if they refuse. Nakia helps Shuri and Williams escape, and Namor retaliates with an attack against the capital of Wakanda, during which Ramonda drowns saving Riri. Namor vows to return in a week with his full army, and the citizens of Wakanda relocate to the Jabari mountains for their safety.

Meanwhile, Ross is arrested by his ex-wife and director of the CIA, Valentina Allegra de Fontaine, for secretly exchanging classified intelligence with the Wakandans. Using a bracelet made from fibers of the herb that gave Namor’s people their superhuman abilities, Shuri reconstructs the heart-shaped herb and ingests it, gaining superhuman abilities and seeing a vision of Killmonger in the Ancestral Plane, who urges her to seek revenge. Shuri dons a new Black Panther suit and is accepted by the other Wakandan tribes as the Black Panther. Despite M’Baku urging for peace, Shuri is determined to exact vengeance on Namor for Ramonda’s death and orders an immediate counterattack on Talokan. Preparing for battle, with Ayo assuming the role of General of the Dora Milaje, Shuri bestows the Midnight Angel armor upon Okoye, who in turn recruits Dora member Aneka to join her. Williams creates an Iron Man-esque powered exoskeleton to aid the Wakandans.

The Wakandans board a seafaring vessel and lure Namor and his warriors to the surface. A battle ensues, and Shuri traps Namor in a fighter aircraft, intending to dry him out and weaken him. The pair crashes on a desert beach and fight. Shuri gains the upper hand, but realizes the similarities between their paths and implores Namor to yield, offering him a peaceful alliance. Namor accepts, and the battle ends. Namor’s cousin, Namora, is upset at Namor’s surrender, but Namor reassures her that their new alliance will allow them to conquer the surface world one day. Williams returns to MIT, leaving her suit behind, while Okoye rescues Ross from captivity.

In Shuri’s absence, M’Baku steps forward to challenge for the throne. Shuri visits Nakia in Haiti where she burns her funeral ceremonial robe in accordance with Ramonda’s wishes, allowing herself to finally grieve T’Challa. In a mid-credits scene, Shuri learns that Nakia had a son with T’Challa, named Toussaint, who Nakia has been raising in secret far from the pressure of the throne. Toussaint reveals his Wakandan name is T’Challa.