Mal (Dove Cameron), Evie (Sofia Carson), Jay (BooBoo Stewart), and Carlos (Cameron Boyce) visit the Isle of the Lost to choose four new villain’s kids (VKs) to take to Auradon. They pick Dizzy (Anna Cathcart), daughter of Drizella and granddaughter of Lady Tremaine (Linda Ko), Celia (Jadidah Goodacre), daughter of Dr. Facilier (Jamal Sims), and Squeaky (Christoan Convery) and Squirmy (Luke Roessler), the twin sons of Mr. Smee (Faustian Di Bauda). The day the kids are to be picked up, Ben (Mitchell Hope), Mal’s boyfriend and the King of Auradon, proposes to her. She accepts; Ben’s ex-girlfriend Audrey (Sarah Jeffery) seethes with jealousy and her grandmother Queen Leah (Judith Maxie) admonishes her for failing to secure the family legacy by marrying Ben.
When the barrier is opened for the new VKs, Hades (Cheyenne Jackson), the god of the underworld, attempts to escape, but Mal beats him back in her dragon form. That night, unable to contain her jealousy of Mal, Audrey steals the Queen’s Crown and Maleficent’s Scepter from The Museum of Cultural History. The theft and Hades’ escape attempt has the citizens panicking. Mal, as future Queen, decides the best way to protect the subjects and restore peace is to close the barrier permanently, meaning no new VKs can come, nor can anyone enter the Isle.
Audrey attacks Mal with Maleficent’s scepter, turning her into an old hag. Mal and the other VKs go to the Isle to get Hades’ ember, the only thing powerful enough to break the scepter’s curse. Mal is restored upon entering the Isle due to the suppression of evil magic there. Celia gets Mal into Hades’ lair, but he thwarts their effort to steal the ember. He is revealed to be Mal’s absentee father and reluctantly gives her the ember, warning her that it mustn’t get wet and will not exhibit its full powers for her. While leaving the Isle, Mal and the others are stopped by Uma, Gil, and Harry, who take the Ember; they agree to help after Mal agrees to release all the children from the Isle.
In Auradon, Audrey attacks Jane’s birthday party with a sleeping curse; Chad (Jedidah Goodacre) obsequiously aligns himself with Audrey, while Jane escapes into the Enchanted Lake. As the entire kingdom falls under Audrey’s spell, she offers to reverse it if Ben will marry her; he refuses, so she turns him into a beast and begins turning people to stone. Mal and Uma (China Anna McClain), vying for leadership of the VKs, return to Auradon with their friends. Despite their bickering, they defeat suits of armor animated by Audrey. Uma finds Audrey’s diary and learns that she spends time at Fairy Cottage, a contribution for which Mal thanks her. Evie, nervous to define her feelings for Doug (Zachary Gibson), wakes him with “true love’s kiss.” Carlos calms Ben, in beast form, until Jane restores him with lake water. As Mal and Uma are thawing towards each other, Audrey traps them in Evie’s house; they reverse Audrey’s spell by combining their magic, and they all reunite there.
At the Fairy Cottage, they find only a shell-shocked Chad. When Mal admits that she plans to seal off the Isle permanently, the group implodes and Celia, learning she can never see her father again, throws the ember in a birdbath, and Uma and Harry leave. After Evie tells Mal how upset she is for lying to her and their friends, they are all suddenly turned to stone, except for Mal. Audrey takes Celia hostage and attacks Mal, who turns into her dragon form. Realizing she is Mal’s only hope, Uma combines their magic to reignite the ember; Mal overcomes Audrey, who falls comatose, and the curses are lifted. The ember could revive Audrey, but only in Hades’ hands; Ben agrees to send for him, while Uma, Harry (Thomas Doherty), Gil (Dylan Playfair), and Celia plan to return to the Isle. Mal apologizes for lying; her friends and former rivals forgive her as they understood that she was just trying to do the right thing. Hades arrives and revives Audrey, but decries the double standard by which Audrey is immediately forgiven because she is not considered a villain. Mal and Ben apologize to Audrey; in response, Audrey and Queen Leah apologize to Mal.
Mal announces that she cannot be the Queen of Auradon unless she can also be the Queen of the Isle because everyone is capable of being good and bad. With Ben and the Fairy Godmother’s agreement, Mal removes the barrier and creates a bridge, and the people of the newly merged society celebrate. Also, Jane (Brenne D’Amico) and Carlos become official, Mal and Ben are engaged, and Audrey has eyes for Harry (after Uma rejects him).
In the mid-credits scene, Mal, Evie, Jay, and Carlos are seen looking at the Isle of the Lost; then racing across the bridge to their parents.
I am so sad that this is supposedly the ending of the Descendants Series. I feel like they could keep going but after the death of Cameron Boyce, who played Carlos, it would be difficult. They would need to write him out of the movie or replace him but it would be hard on both us fans and his co stars. Just like the first two Descendants movies, this film is equally as good. I mean all the songs, the dancing, the character developments. Yet again longing for more. Signing off with my favorite song