Everyone heads towards the Giant Rock, the Shuriken telling them where to go in order to rescue Chespie. Mairin, Bonnie, and Serena look on at the Rock. The Rock uses vines to attack, but Pikachu and Charizard counter with Iron Tail and Flamethrower. More vines attack as Malva, Blaziken Mask, and Alain order their Pokémon to use Flamethrower. Valerie and Olympia help as Ash and Alain make their way through the vines. Valerie is soon captured, but she insists they continue. Korrina and Lucario stop a vine from attacking Greninja, but are also captured. They, too, insist the others continue on. Ramos and Gogoat also buy them time before being captured. Alain and Ash are captured by vines as well, but Viola frees them with Vivillon's Solar Beam. Grant has Tyrunt attack the vines with Rock Tomb, creating a wall, but more vines attack Viola, which knocks her into Grant and then captures them. Ash and Alain climb up the wall as more vines attack, but Wulfric has Abomasnow use Ice Shard on them to freeze the vines. He then orders them to hurry up as Abomasnow is knocked away. Their friends go ahead to clear a path as Malva has Houndoom use Dark Pulse and Professor Sycamore has Garchomp use Dragon Rage. Afterward, both are captured by the vines. They tell Ash and Alain to keep going, and Ash promises not to let them down. Watching with Serena and Bonnie, Mairin hopes that Chespie will be okay. Clemont has Chespin, Luxray, and Bunnelby attack the vines with Pin Missile, Swift, and Mud Shot respectively to help clear a path.
As Alain and Ash approach the centre, a vine rises up to attack them, but it is hit by Bullet Seed. Ash looks up and is surprised to see Team Rocket in a helicopter with Gourgeist having launched the Bullet Seed. Jessie tells Ash to not just stand there, but a vine rises up and attacks the helicopter, sending Team Rocket flying. Gardevoir uses Psychic to save them. At a Pokémon Center, Sawyer, Trevor, Shauna, and Tierno watch the action unfold on TV as Diantha and Steven Stone assist with their Pokémon, Gardevoir and Metagross. The two Pokémon use Psychic to wrap up the attacking vines. They continue to attack the vines, but Steven and Diantha find themselves trapped as Blaziken Mask and Blaziken are attacked. Squishy and Z2 observe the battle, with Z2 expressing surprise that they are continuing to fight. Squishy tells Z2 that it knows not all humans are bad after having watched the humans on their journey. Reaching the centre, Ash orders Pikachu to use Electro Ball and Greninja to use Water Shuriken as Alain orders Charizard to attack with Flamethrower. The attacks are blocked with vines, but with support and determination, they break through and enter the rock. They spot Chespie lying overhead, and Alain goes to free Chespie, only for crystals to block his path. Ash promises to cover Alain as best as they can whilst he goes to free Chespie. As another crystal goes to attack, Ash orders Pikachu to use Electro Ball and has Greninja use Cut, which cuts through the crystals. Outside, the Rock continues to move as Serena commands Braixen, Pancham, and Sylveon to attack. The vines surround them, and a vine goes to attack Mairin. As Alain nears Chespie, another crystal looms in front of him, but Ash orders Greninja to use Water Shuriken, which breaks the crystal. As more crystals appear to attempt to stop Alain, he reaches Chespie. Outside, the vines are about to hit Mairin when they stop. The rocks also stop moving. Ash and Alain, along with their Pokémon, emerge from the Rock, having freed Chespie. Everyone looks on, pleased that the crisis has been averted.
Mairin hugs Chespie, who is still unconscious, and thanks Alain for his work. Steven says all they have to do now is to destroy the Rock. As Team Rocket films the scene, all of their Pokémon launch an attack on the Rock, which knocks it down. Ash wonders if the attack worked, but the Rock recovers while Lysandre appears, vowing to still destroy the world. Lysandre has the Rock launch an attack at the group, but Valerie has Spritzee use Light Screen, which minimizes the damage. As everyone recovers from the hit, Bonnie and Clemont are surprised when Blaziken Mask's mask comes off, revealing that he is their father. Meyer has been injured, but insists he is alright as the giant Rock begins moving forward again. Alain wonders how they can stop it, and Clemont points out the device on Lysandre's wrist. Alain realises that they have to destroy it. As everyone prepares to fight, Z2 notes that they are actually prepared to fight. Squishy informs Z2 that neither humans nor Pokémon will give up, even though Z2 feels they are too weak. Squishy says that their real strength lies in working together, caring about each other, and having the power to believe in themselves and find the will to succeed. The Rock launches another attack that sends them all flying. Seeing this, Z2 decides to believe in them as Squishy does, and they both jump down from Bonnie's arms. Bonnie moves to go after them, but Meyer stops her as the Cores confront the Rock. They call on every Cell in the world as everyone watches them become Zygarde Complete Forme. Seeing Zygarde, Olympia recognises the deep green eyes from her prophecy. Lysandre notes that they hid this Forme from him and confronts Zygarde, saying it must have seen what this world is like and wonders what could be worth defending. Zygarde states this world belongs to the others and is protecting them. The Rock launches another attack, which is countered by Dragon Pulse. The Rock sends more vines towards Zygarde, who dodges before attacking with Extreme Speed. Seeing their chance, Ash and Alain order Pikachu, Greninja, and Charizard to use Thunderbolt, Water Shuriken, and Flamethrower respectively on Lysandre. The device falls off of Lysandre's wrist. Zygarde manages to break through the Rock with Extreme Speed before attacking the Rock with Core Enforcer, destroying it. Lysandre, who refuses to accept that he has been defeated, falls into the explosion, ending the crisis once and for all. Those watching along on TV cheer.
Diantha thanks everyone for their help as Steven wonders what became of Lysandre. Malva doesn't care and heads off, telling Steven to let her clean up Team Flare before turning herself in to Officer Jenny. Chespie wakes up from its coma, which makes Mairin happy as she thanks Alain for his help. Alain is pleased that Chespie is safe and asks Mairin to forgive him. Zygarde approaches Ash and his friends as Squishy thanks Bonnie for looking out for it. Zygarde then restores order to the world, removing all the vines from Lumiose City and causing the red sky to disappear. Once the world is restored, Zygarde disassembles, leaving Squishy and Z2 floating in the air. Chespie approaches Squishy, who remembers that Chespie freed him from Lysandre Labs and expresses its gratitude. Squishy thanks Bonnie for taking it on a journey, allowing it to see that humans can be trusted to protect the world. Bonnie realises that Squishy is saying goodbye, and Squishy confirms it must leave to restore its energy. Squishy and Z2 rise into the sky, sharing a fond farewell with their friends as they both disappear into the sky. Bonnie tells Squishy how much it means to her. Just after they leave, the sun rises over Ash, Alain, and their friends, who all helped to save Kalos and the world from Team Flare.