The full story
Attilan is a city of Inhumans hidden on the Moon. Its king, Black Bolt, can't speak, because his voice destroys whatever hears it; his queen, Medusa, who fights with her living hair, speaks for him. His brother Maximus came out of Terrigenesis with no powers at all, which in Attilan's rigid order makes him nobody, and he wants the throne.
Maximus stages a coup. Gorgon, who sends out shockwaves with his hooves, has already gone down to Earth to look for Triton, who vanished on a mission to Oahu. Maximus shaves Medusa's head to take her power, and her sister Crystal has her giant teleporting dog Lockjaw send the family to safety. Black Bolt, Medusa and their cousin Karnak, who sees the flaw in everything, all land in different parts of Oahu. Crystal is left behind as Maximus's prisoner.
Black Bolt is arrested in Honolulu and ends up in the lab of Evan Declan, a geneticist working for Maximus, who wants his DNA. Medusa, powerless, joins up with Louise Fisher, a scientist at Callisto Aerospace who has been tracking strange signals from the Moon. Maximus sends Auran, his new head of the Royal Guard, and a team of Inhumans to hunt them. Crystal escapes to Earth with Lockjaw, who is hurt in the landing.
The family finds each other piece by piece. When the Inhuman Mordis brings Declan's facility down on all of them, Gorgon dies saving the others, and Karnak brings him back through a second Terrigenesis with Auran's healing DNA; he wakes up feral. Triton turns up alive. Black Bolt, who saw the coup coming, takes the family back to Attilan to bargain with Maximus, who breaks the deal as soon as he can.
Maximus has rigged Attilan to destroy itself unless he keeps it in check. Black Bolt evacuates the city's people to Earth through Eldrac, a living doorway. Maximus admits he forged the letter that made a teenage Black Bolt cry out and kill their parents. Black Bolt seals him in a vault, and leaves Attilan to fall. On Earth, he and Medusa address the Inhumans they've brought with them.