The movie begins with a funeral scene. T'Challa will die of an illness and will have a whole moment dedicated to him, but it's really a tribute to Chadwick Boseman.
Lake Bell plays an undercover American scientist who's supposed to be Riri Williams' teacher. She knows about the girl's potential and gives advice about what Riri can do using her intelligence.
Riri Williams is an MIT student prodigy who befriended Shuri while in the US and went to Wakanda. She created a device that finds Vibranium.
Namor was born in 1500. He's the son of a human explorer and an indigenous princess from an indigenous society called Tialocan.
He fought against the Spanish Inquisition, but his kingdom suffered greatly, which led them to hide underwater. He will be half-mutant/half-Tialocan (a people described as magical).
Shuri refuses to ascend to the throne, so Ramonda remains as queen regent. She will be very depressed after her family’s losses.
Lake Bell's character uses Riri's creation to locate Vibranium and discovers it in Antarctica and the Atlantic Ocean. However, the Vibranium ends up awakening Tialocan and the explosion damages Namor's kingdom, which was already screwed since 1500.
The Vibranium explosion kills some Tialocans and Namor gets pissed off, going to Wakanda wanting them to pass over the technology to repair his kingdom, but with ulterior motives, such as destroying Spain and other countries.
Namora and Attuma try to capture Riri, who escapes by creating an armor made out of wrecked cars.
Okoye and Nakia save Riri from the chase that goes on for most of the movie. Riri is very important to the plot. They take the girl back to Wakanda. Namor then decides to invade the country.
Namor floods all of Nigeria, causing a genocide just to get to Wakanda, which is also affected by a tsunami that kills thousands, including Queen Ramonda.
Shuri becomes extremely distraught and creates a synthetic vibranium heart herb and distributes countless vibranium suits to Riri, Okoye, Nakia, Aneka and M'baku, all of whom will fight Namor.
Shuri will try to go to the astral plane to find her brother, but it's Killmonger she sees and he's remorseful. He teaches her how to become a Black Panther.
Meanwhile, the US finds out that Queen Ramonda has died and decides to break ties with Wakanda, declaring war on the country.
Namor vs Shuri. M'baku, Okoye and Aneka vs Attuma. Nakia and Riri vs Namora. The Tialocans are very strong, all the Dora Milaje's needed for assistance in the fight.
Namor is defeated by Shuri, who's the new Black Panther. He retreats with his people. Shuri passes the mantle on to M'baku, who becomes king and Black Panther. Shuri stays focused only on the lab.
Post-credits scenes: Dr. Doom appears at the end being the orchestrator of the Wakanda vs Tialocan war. He's the one who hired the American scientist, who's revealed to be Lucia Von Bardas.
Nakia is pregnant with a boy from T’Challa and the Vibranium in Antarctica leads to a mission for Wakanda to go rescue it. Plot twist is that the Thunderbolts are also sent by the US, they are: Ghost, Yelena and John Walker.