Top competitors from past seasons get separated into groups of villains of heroes based on past performances on the show. From then on, they compete against each other to win the 1 million dollar prize.
The players gather on the beach to dig up 3D puzzle pieces and use them to assemble an international landmark. But that's easier said than done when Alejandro can't use his legs, the rest of his Villainous team refuses to work together, and the Heroes struggle to keep up as Sam flails and a head injury makes Mike lose access to his alternate personalities.
The Heroic Hamsters and the Villainous Vultures race into the forest to collect unusual paintball weaponry and use it to pick off the other team - last team standing wins! But a straightforward challenge becomes twisty when a Hero makes a villainous move, and a Villain acts decidedly heroic.
Chris combines a pancake eating contest with an obstacle course in the ultimate tummy twister. Meanwhile, sparks fly between newly Villain-ized Courtney and Scott, newly Heroic Duncan has a serious crisis of bad boy confidence, and someone mysteriously breaks Sierra's smartphone, sending her into a serious case of Cody withdrawal.
During a race across the island, the local wildlife is radically altered by the rare blue harvest moon and even the littlest bunny becomes a blood-thirsty predator. Heather and Alejandro lock horns, Cameron dodges Sierra's deluded affections to help Mike with his newest multiple personality problem, and Gwen is getting more homesick by the minute.
The teams travel to Boney Island for an egg hunt inside The Fun Zone, which is anything but fun! New Villain Cameron bonds with Gwen, Heather finally trusts Alejandro enough to team up with him, and Zoey begins to doubt her faith in Mike when she suspects his new malevolent personality is taking control.
Chris orchestrates a brutal boxing free-for-all that pits the All-Stars against their biggest, baddest enemies. For most, this means facing off against one of the island's dreaded mutants - but one All-Star has to battle his oldest nemesis, and two best friends are forced to battle each other!
The challenge is a simple life-or-death boat race around the island, but things get complicated when Chris messes with the team dynamics. Plus, Zoey puts her life in danger to rescue Mike from his alter ego, and Duncan devises a bad-boy scheme that's downright explosive.
The 100th episode celebrations are cut short when Ezekiel kidnaps Chris and the All-Stars head out in search of their host. Meanwhile, Alejandro finds a saboteur in their midst, and a few misplaced kisses have dire consequences.
The All-Stars face the Boot Camp from Hell as they struggle to survive the harshest obstacle course ever. Meanwhile, alliances are pushed beyond their limits, and the two most evil All-Stars wage a war for survival as one finally speaks the truth while the other spins a web of lies.
The final five All-Stars race to the most dangerous regions of the island to find ingredients for the ultimate sundae. Meanwhile, multiple relationships are shattered when one All-Star's secret plans for ultimate victory are revealed.
Zoey gives up hope that she'll ever see Mike again and tells Mal the jig is up. With a little help from some of the previously eliminated, Mal and Zoey face off in a horrifying final challenge called Circles of Doom. It causes more chaos than anyone expected and results in the sinking of the island.
Great news: Sky likes Dave! Bad news: Not nearly as much as Dave likes Sky. Spooked by a possible zombie sighting, Shawn bolts and puts his team in jeopardy. A surprise visit from a past competitor raises some very serious questions about a previous elimination.
Chris merges the teams and feeds them some expired meat before the first nighttime challenge. Dave finally hears what Sky's saying, and Jasmine finally sees how Shawn's feeling. Scarlett learns the truth about Pahkitew Island!
With the island becoming wildly volatile and deadly, Chris sends the teens underground to shut it down. Scarlett has a different plan, and with only minutes to spare before Pahkitew explodes the rest of them have to stop her.
With luck on his side, Shawn gets to bring Jasmine back as his helper. Sky gets stuck with Dave. Halfway through the challenge Jasmine and Dave learn some shocking truths about their partners, and the helpers become hurters!