"...And Finally: Black Bolt" starts off with Maximus explaining his failsafe to the Royal Family. If he doesn't place his palm on the control, Attilan's protective dome will fail and expose all of Attilan's residents to the elements of space.
Black Bolt signs to Medusa that she and Crystal need to start an evacuation of Attilan while he and Triton begin to investigate Maximus' device.
Lockjaw teleports Medusa to Earth so that the Queen can get help from Louise. Louise agrees to help out if, and only if, she can go to Attilan.
The Royal Guard finds Karnak and throws him in Black Bolt's quiet chamber.
A recently-revived Gorgon is on a rampage in the Terrigenesis chambers on Attilan. He finds Dr. Declan and throws him across the room, mortally wounding him. The Royal Guard runs in and an Inhuman uses her powers to render the hooved Inhuman unconscious.
Maximus leads Black Bolt and Triton to his device but on the way, the group runs into a squad of Royal Guardsmen. Triton is left to find them off while Black Bolt takes Maximus through the tunnels.
Gorgon gets thrown into the quiet room with Karnak and begs him to help.
In the tunnels, Maximus confronts Black Bolt about the kingsmanship. Attilan starts shaking as the dome starts weakening.
Gorgon tries going on a rampage and Karnak combines their powers to break through the Quiet Room.
Crystal approaches Eldrac and warns him of an impending evacuation.
Black and Maximus make their way out of the tunnels, but run into another squadron of the Guardsmen. Black Bolt holds them off but Maximus gets away.
Karnak and Gorgon run into Triton in the hallway.
Maximus is on his way to the Terrigenesis chambers so he can undergo the procedure again, but they find Declan dead on arrival. Someone has taken the Terrigen crystals.
Maximus touches Bronaja so he has a vision — and Bronaja sees Maximus as the undisputed king of Attilan. Maximus starts broadcasting to fellow Inhumans on Attilan, trying to rally them for a final push against Black Bolt and the Royal Family.
Medusa and Louise
Medusa gives Louise the crate full of Terrigen to safeguard on Earth. Medusa and Crystal can't take Louise to Attilan, but Louise convinces Medusa to take the vial Louise has kept that have her father's ashes in it.
Karnak, Gorgon, and Triton are working on stopping the failing dome when Black Bolt runs in and gets mad the Karnak went behind his back to revive Gorgon.
Karnak talks Black Bolt down and reveals that he can't think of a way to stop of the failing dome. Black Bolt, Karnak, and Gorgon meet with Medusa to discuss the evacuation while Triton stays back in the control room.
Medusa tells the group that she wants to try negotiating with Maximus one last time. She took one of the Terrigen crystals from the safe she gave Louise to use as a bargaining chip.
Medusa asks Maximus if he's willing to die for his cause and the two talk about the different sides of the equation. Medusa admits that if she had been a better friend to Maximus, they wouldn't be in the predicament they are.
Maximus reiterates the fact that he wants to be king and Medusa brings up the point that if he loved Attilan, he wouldn't destroy it.
Maximus tries convincing Medusa to go back to Earth, but she shows him the Terrigen crystal she has. She says she'll give it to him if he steps down from the throne, something he doesn't agree to.
Medusa throws the crystal against the wall, crushing it and ruining Maximus' chances at undergoing Terrigenesis. Maximus calls Auran in to kill Medusa and she reveals she can't because she promised the Queen safety.
The Royal Family gathers again and Black Bolt orders the evacuation of Attilan.
Medusa gathers the residents of Attilan to give an address. While she admits to mishandling the rule of Attilan, she tells them they always had the best interest of the community at the forefront.
The Royal Family tells the citizens that Maximus has compromised the dome and they need to evacuate.
Maximus, looking on, vents his frustration to Auran calling Attilan his. Auran is quick to remind him that Attilan is "theirs."
She tries convincing him to put his hand on the scanner in the control room, but Maximus cites Bronaja's vision of him being the undisputed king of Attilan. Maximus orders Auran to stand guard outside his door.
Medusa takes the vial Louise gave her and buries it among the rubble of one of the buildings that fell in Attilan.
Karnak notices Gorgon missing from the crowd and goes to find him. He finds him wandering near the throne and reminds him that if he stays on Attilan, he will die. Karnak says if Gorgon comes with, he'll help him return to his previous state.
Karnak and Gorgon join the rest of the Royal Family in the throne room. Black Bolt sits on the throne one last time and tells the group that he needs to stay behind and resolve this problem with Maximus. A tearful Medusa kisses her husband before Lockjaw teleports the entire Royal Family, sans Black Bolt to Earth.
Black Bolt approaches Maximus in the control room. Maximus shares that it's too late for them to save Attilan. Maximus begins to tell Black Bolt the history of their family — Maximus forged the genetic council documents that caused Black Bolt to mistakenly kill his parents.
Maximus steps back and spreads his arms out and tells Black Bolt to kill him. Instead, Black Bolt knocks him out and takes him to the bunker. There, Maximus realizes that the bunker will be able to withstand the collapse of the dome. Black Bolt pushes Maximus aside and runs out of the bunker, locking his brother inside.
Black Bolt goes out to the courtyard, and says "Goodbye brother." and destroys the building on top of the bunker, ensuring Maximus is trapped.
Black Bolt runs to Eldrac and is able to teleport to Earth immediately before the fall of Attilan.
The dome fails and is exposed to space. We see the throne on Attilan start
Lockjaw is panting on Earth. He's teleported the Royal Family to a safe location. The family is dressed back into their uniforms and they're about to address their people again.
Medusa starts talking to the people of Attilan and welcomes them home. She states that they have an uncertain future but have come back to their rightful birthplace.
The season ends as the Royal Family turns back to look up at the moon.