"Ride with the tide!
Deep beneath the waves, King Triton's powerful trident has passed through the magical barrier that surrounds the Isle of the Lost-keeping villains in and magic out, and when Mal's longtime rival Uma, daughter of Ursula, gets wind of this, she can't believe her luck. The tide has dragged in something good for a change, and Uma is determined to get her wicked hands on it. But first, she needs a pirate crew.
A storm is brewing back in Auradon, and when Mal, Evie, Carlos, and Jay hear that the trident has been washed away, they realize they'll have to find it before anyone from the Isle does. Luckily, they seem to have a talent for locating missing magical objects.
As Uma readies for the high seas alongside Harry, son of Captain Hook, Gil, son of Gaston, and the toughest rogues on the Isle of the Lost, the reformed villains of Auradon devise their own master plan, and with King Ben away on royal business, they won't have to play by all the rules. Using bad for good can't be totally evil, right?
The thrilling, perilous race to the trident pits old friends - and current enemies - against each other with the future of Auradon on the line. Both teams might like to make waves, but only one will come out on top of this one."
Years ago, on the Isle of the Lost, Mal wasn't just friends with Mad Maddy; she also teamed up with the daughter of the Sea Witch, Uma for all kinds of mischief. However, an attempt to prank the especially mean Cruella De Vil leads Mal to seemingly fall off the docks and into the water. Uma laughs at her instead of saving her, only for Mal to surprise her and dump a bucket of shrimp on Uma in return. No matter how much Uma tried to wash her hair, the disgusting smell never left her hair. Mal then got everyone to call Uma the name Shrimpy.
Fast-forward to Descendants, Uma watches Carlos, Jay and Evie board the royal limousine to be taken to Auradon for a chance at a better life. Uma seethes with envy when she finds out that Mal was also chosen. From that day forward, she vowed to get off the island and into Auradon.
Then came the day of Prince Ben's coronation. Jane stole the wand to give herself a makeover, but the magic of her mother's wand flew out of control and made a hole in the island's barrier. Maleficent escaped to conquer Auradon. Everyone else attempted to leave, but found that the barrier was back in place. The villains watched the A.N.N., learning Maleficent had been turned into a lizard and that Mal, Jay, Evie and Carlos had turned their backs on evil and were celebrating.
And now, the present day, a few days after the last book.
All of Auradon's kingdoms hold celebrations, which lead up to the cotillion, in honor of the U.S.A.'s founding. Watching Sebastian lead a wonderful musical performance are none other than the VKs, having been invited by King Ben. Evie has also gained a new friend in Arabella, niece to Ariel; Arabella copies Evie's outfits, although in shades of lilac. The celebration suddenly comes to an end when an unexpected storm strikes. Fearing it may be the disabled talismans of evil, the VKs decide to have Fairy Godmother destroy them before anything else happens. Retrieving her wand from the museum, Fairy Godmother improvises a version of Bibbidi-Bobbidi-Boo to destroy the talismans. However, this releases a burst of wild magic, which briefly causes the Isle of the Lost's dome to disappear; though since it's invisible to the islanders, no-one noticed.
The next day, Ben is called away on royal business because Agrabah and Northern Wei are having a dispute that could end in violence. The Auradon Knights win against the merman team, elsewhere. Carlos convinces Jane to attend the cheerleader tryouts as she's better suited for it than being the Fighting Knights mascot. At the same time, Jay joins the R.O.A.R. (Royal Order of Auradon Regiment) team, being coached by Lonnie's older brother Li'l Shang. Evie finds Mal using her spell book to avoid detention for being late to class, scolding her. They later find Arabella upset, and learn that she caused the storm yesterday by trying to use her grandfather's trident. However, she lost control of it and it flew away. The VKs decide to help find it.
Back on the Isle of the Lost, Uma learns that a goblin saw the trident fell into the waters of the isle when the barrier briefly vanished. Everyone is looking for it; even if it isn't magic, it can be used to barter one's way off this accursed prison. Uma decides that it's time to put together a crew to work for her, hearing Captain Hook is hosting a race and will give the Lost Revenge to whoever wins. She joins the race, convincing Harry Hook to be her first mate; they win the Lost Revenge, recruiting Gaston's son Gil and other rogues. Uma learns from her fellow employee at the shop that Yen Sid knows where the pieces of Ursula's necklace are; once it's re-completed, it will be able to seek out the trident like a magnet.
Harry's research reveals that Yen Sid brought his intern, Sophie with him to the island when he relocated; this is the only weak link they can work on, since Yen Sid will never give in to intimidation and torture. Claiming to have found something Sophie lost, Gil lures her to chip shop. After a mind-numbing hour of listening to Sophie talk, Gil begs Uma to step in. Uma inquires what Sophie is searching for, remaining vague as to whether or not she can provide it. Sophie reveals that Yen Sid's hat was taken to be mended at the hat shop, but it got sold to someone else; the sorcerer mainly uses it to hide his bald spot, since its magic is neutralized by the barrier. Remembering Gil bought it, Uma takes it from him and threatens to burn it unless Sophie tells her when the necklace is. Sophie relents and tell her its hidden on the Isle of the Doomed.
In Auradon, Ben arrives at Northern Wei, finding that his old friend Charlie Wong is the elder of Stone City. He learns that olives from Agrabah have been falling over the great wall and that the flying carpets give off sonic booms. Ben and Lonnie decide to talk with the royal vizier of Agrabah, who is shocked by how humble Lonnie is. (She is the daughter of the famous Mulan after all.) Deciding a compromise is best, Ben gets the permission of the sultan and emperor to build a great door into the wall to allow Agrabahians to come and go as they please; the two societies decide to exchange tips on agriculture as well. Before he can leave, Ben is swept into a magical whirlwind as a familiar voice tells him that he is needed elsewhere...
Back to the VKs, they attempt to "borrow" a speedboat from the royal marina, but are caught red-handed by Fairy Godmother; she refuses to listen to their reasons, simply believing they couldn't resist misbehaving. Escorted back to Auradon Prep, they pass Jane, who distraught at the idea of them leaving. Right before Fairy Godmother can punish them, Ben arrives and gives the cover story of the VKs working on a secret mission for him. After explaining the situation, the VKs learn that Jane had Merlin bring him back to prevent their expulsion. They take the speedboat out to the isle of the lost to get the trident back.
On the Isle of the Doomed, Uma and her crew find Yen Sid's "map" and find a trove of magic items. Uma finds her mother's seashell necklace and puts it back together; however a piece is missing. She then realizes a piece of the shell was in her pendant; Ursula had vaguely told her it was all she had left, but not of what. With the shell completed, it begins leading Uma to the trident. She finds it's location, and swims down to get it. Outside of the barrier, Mal and the others arrive; she reverses time by a few minutes, keeping Uma away from the trident. Using her own spell, Mal pulls the trident into her hand, but loses her glove to the pull of the seashell necklace. The VKs succeed in their mission, leaving Uma fuming; she ended up with Mal's glove instead.
Back in Auradon, the trident is returned to the museum. Evie and Mal are also asked to handover their magical heirlooms, so they can be kept safe in the museum; Evie gives up her mirror, while Mal decides to give up her spell book the next day but thought against it. Carlos runs into Jane, who was accepted as a cheerleader; Carlos realizes that Jane doesn't have a date for cotillion, so he's thinking about asking her if she wants to be his date. Jay joins the R.O.A.R. team and replaces Chad Charming as the captain. Seeing that she needs to try looking the part of royal girlfriend, Mal asks Evie to start giving her a makeover. Ben asks her to the cotillion, where she will gain the title of Lady; Mal accepts, asking to keep her mother in her room.
Back on the Isle of the Lost, Uma decides to bide her time until she can get revenge.
- Several details about the Descendants universe are revealed:
- Agrabah is next to Northern Wei, which is the equivalent of China from Mulan.
- A new Auradon sport is introduced: R.O.A.R., a mixture of parkour and fencing. The captain is decided by however beats the current one. In the novel, Jay replaces Chad (the current captain).
- The team is made up of nine members max; however, Ben had to quit as his King duties left no free time to play.
- Genie, Grumpy and Merryweather are confirmed teachers for Auradon Prep.
- Merryweather teaches life skills, including how to use a checkbook.
- A third school exists on the Isle of the Lost: Serpent Prep.
- Though a yellow energy is clearly visible from outside of the Isle of the Lost, the interior of the barrier is invisible to the inhabitants of the island.
- New characters are introduced:
- Harry - son of Captain Hook and brother to CJ and Harriet.
- Gil - son of Gaston and brother to Gaston Jr. and Gaston the Third.
- Uma - daughter of Ursula and the sister to the Sea Witches.
- Sophie - Yen Sid's intern from Auradon.
- Sophie is described as "mousey"; this is a nod to Mickey Mouse, who is known for his role as Yen Sid's apprentice.
- Arabella - Ariel's niece.
- Li'l Shang (Li Shang Jr.) - Mulan and Shang's son and Lonnie's older brother.
- The VKs are shown to have strong will-power, as noted by Fairy Godmother.
- They were able to resist being tempted by the talismans' power. However, as each of them felt poorly after the destruction of them, it seems that the VKs would have been gradually turned back to the side of evil if the talismans hadn't been destroyed.
- Going by Arabella's comments, it seems mermaids gained the ability to turn into humans once on land.
- It is revealed that Audrey dumped Chad Charming.
- As Audrey originally only started dating Chad to try making Ben jealous to get him back from Mal, this result ended up being not much of a surprise.
- Evie hands over the Magic Mirror to the museum.
- Mal's favorite flowers are bat orchids and black dahlias.
- Freddie Facilier is oddly absent from the story; this could perhaps reflect that her original voice actress China Anne McClain plays Uma in Descendants 2.
- Beast and Belle are still out on their cruise.
- It's confirmed that while their cruise has lasted about a month, the rest of the story has taken place months later.
- Evie names her clothing designs as Evie's 4 Hearts.
- At the end of the story, Mal asks to keep her mother's prison in her room, effectively keeping Maleficent as a pet.
- There exists a sport called R.O.A.R. (Royal Order of Auradon Regiment) in Auradon. It's the sport of the next sport season at Auradon Prep. The Tourney season ending in this book.
- Mal starts trying to look the part of royal girlfriend at the end of the story; however, Descendants 2 shows that the pressure of trying to be someone she's not got to be too much for her.