Our heroes are battling hard against a group of mind-controlled Pokémon, and Lusamine is still resisting rescue. When Gladion realizes their attacks won’t stop until the Ultra Beast is defeated, Ash suggests the two of them use Z-Moves.
Instead, Gladion and his Pokémon provide a distraction while Ash and Pikachu use a powerful new Z-Move: 10,000,000 Volt Thunderbolt! This finally defeats the Ultra Beast, and after Lillie pleads with her mother to wake up, Lusamine is finally herself again.
Returning through the Ultra Wormhole, our heroes and Lusamine are reunited with Professor Kukui and Professor Burnet, and Lusamine gratefully gives credit to our heroes for saving her.
After Lillie narrates the events of the previous episode, Lusamine creates more boulders to protect herself, but Nebby smashes through them. She continues to demand them to stop before emitting a pulse into the air. Eventually, Ash and Pikachu catch up, but Lusamine fills the area with a lake of poison lake.
Meanwhile, Gladion watches his stalled Pokémon as Lusamine's Absol uses another attack. In order to change the tide, he throws a Fire Memory to his Silvally, and its type changes to Fire. Silvally's fiery aura melts the ice and frees its trapped legs. At Gladion's command, it launches a Multi-Attack at Absol. The attacks hits and frees Umbreon and Lycanroc from Absol's earlier Mean Look. Silvally attacks Absol with Crush Claw, pushing it away. Absol retaliates with Ice Beam, but the attack is intercepted by Umbreon. Gladion has Silvally use Air Slash, then uses his Z-Ring and passes the Z-Power onto Lycanroc, who uses Continental Crush.
Lana, Mallow, and Sophocles step back as Lusamine's Pokémon continue to approach. The trio refuse to attack out of concern for Rowlet, who remains attracted to Lilligant's scent. Mallow follows Sophocles' suggestion, and has Steenee use Sweet Scent. The plan works as Rowlet flies over to Steenee, who defends herself from its advance. Steenee suddenly has an idea and has Mallow toss her into the sky. She strikes Rowlet with her sepals, which sends Rowlet into Lilligant. Lana dubs the combination a "Rowlaunch" and Mallow immediately adopts the name. Liligant then begins to charge up a Solar Beam, but Litten quickly knocks it out with Fire Fang. Then, Sophocles has Togedemaru and Charjabug use Zing Zap and Discharge, respectively, on Milotic, defeating it. Lana readies her Popplio and activates her Z-Ring to perform Hydro Vortex, which defeats Lusamine's Mismagius. However, Lusamine's Pokémon simultaneously stand up again.
Gladion's Lycanroc uses Stone Edge to intercept Absol. Gladion realizes that the battle will continue on until Lusamine is released. He leaves Umbreon and Lycanroc to handle Absol and mounts Silvally to confront his mother. Meanwhile, Lusamine continues to warn Ash about coming closer. He responds, claiming her children will arrive shortly. This only inflames the situation as Lusamine makes a wave out of the poisonous liquid. Nebby scoops Ash and Pikachu up in its mouth and spares them from the deluge. Ash then mounts on its back and Nebby runs across the poison lake, avoiding Lusamine's attacks as they confront her. Ash has Pikachu distract Lusamine with a Thunderbolt and Electro Ball as he continues to run towards her. Ash jumps towards Lusamine, who promptly swats him away with her tentacle. The duo try the same tactic, with Pikachu launching another Electro Ball, but to no avail, as Ash is struck several times. Lillie and Gladion eventually catch up to Ash, along with Snowy, Silvally, Ash's Lycanroc, and Lusamine's Clefable.
Lusamine exclaims her hatred and proceeds to attack, but Nebby protects Ash from it. Ash thanks Lillie, who explains that she was able to snap Clefable out of the Ultra Beast's control. Gladion alerts Ash that Lusamine must be stopped because her Pokémon continue to recover even after their defeat in battle. Nebby and Ash's Lycanroc leave the scene to confront Lusamine's Pokémon. Lillie and Snowy are carried over to Ash by Clefable thanks to its Magic Guard. Gladion soon joins them after he installs a Steel Memory into Silvally, and rides across the lake without being poisoned. Now on the other side, Gladion exclaims he has trained Silvally to battle the Ultra Beasts. Lusamine raises the ground level around her to avoid further confrontation, though Lillie begins to climb the ascent. She wishes to tell her mother something, demanding that Gladion remain behind. He watches on, though he intends to make a move with Ash in case danger strikes.
Lillie reaches Lusamine, who continues to create more obstacles until Lillie yells out that she hates her. She scolds Lusamine's behavior as spoiled and childlike, ever since she fused with UB01: Symbiont. She recognizes that the fused Lusamine is not her mother, but a puppet for the Ultra Beast. Lillie requests her mother's return and notes her strength, raising her hand in anticipation. Lusamine briefly regains control, muttering Lillie's name and reaching her arm out. However, the Ultra Beast regains its control and grows to a larger size. Gladion and Silvally jump to save Lillie before she is hit. The Ultra Beast promptly surrounds itself with more defensive boulders.
Gladion fears UB01: Symbiont does not want to let go of Lusamine, noting that the pair has too much interest in each other. As the Ultra Beast emits more rocks and spikes, Ash suggests he and Gladion use their Z-Moves together, but Gladion explains that he used Continental Crush on Absol earlier. Instead, he and Lillie will distract its attention for Ash to have a clear shot. Ash braces Pikachu to attack, but his Electrium Z suddenly sparks with electricity. Ash's hat is blown away and he notices the odd Z-Crystal, shaped like Pikachu's tail; a Pikashunium Z. Ash then presses his Z-Ring and fist-bumps his Pikachu, who now wears his cap. Ash passes the Z-Power to Pikachu, making a normal Thunderbolt 100 times stronger. Pikachu performs the multicolored 10,000,000 Volt Thunderbolt and fires it on the Ultra Beast, lighting up the sky with a large yellow beam. As the dust settles, the odd-looking Z-Crystal returns to an Electrium Z and the Ultra Beast collapses soon after.
Lillie, Gladion, and Clefable rush to Lusamine's side. They notice her trembling hand and pull her out of the Ultra Beast's body. Nihilego also emerges and flies away, leaving Lusamine now covered in black ink. Pikachu returns Ash's hat to him. Lusamine wakes up and her Pokémon snap out of the Ultra Beast's control, whereupon Sophocles concludes that they won. As Lusamine stands up with the help of her children, Lillie commends her strength, and Lusamine admits that it felt like a nightmare until Lillie's voice called her out. She apologizes for her actions and embraces her children, making Lillie cry as well. Lusamine's Pokemon and the others soon join Ash, Lusamine, Lillie, and Gladion. When Rotom expresses curiosity about the yellow beam that had been shot in the sky, Ash explains that it was their new Z-Move, 10,000,000 Volt Thunderbolt. This astounds Rotom, who hopes to hear more.
At the Altar of the Sunne, Professor Burnet, Professor Kukui, and Team Rocket, who were sleeping, notice the Ultra Wormhole, and Nebby arrives with the group on its back. When Lusamine and Kukui thank the children for their efforts, the class proclaims they are the best team ever. Meanwhile, Team Rocket expresses their gratitude that everything went fine and are then carried away by Bewear. As the Ultra Wormhole disappears, Sophocles reveals that he took a rock from Ultra Space as a souvenir. Lana scares him into thinking the stone will summon an Ultra Beast, but she soon admits it was a joke.