A Pheromosa emerges from an Ultra Wormhole over Melemele Island and runs into the forest. Meanwhile, Hala is busy working on his Z-Ring when he encounters Pheromosa. Soon, Professor Kukui wakes Ash up and alerts him to an emergency dispatch. The Ultra Guardians are all picked up by their respective Ride Pokémon, just as Hala's Hariyama is defeated by Pheromosa. The Ultra Beast then waltzes into Hala's home and grabs his Fightinium Z. The Ultra Guardians arrive on the scene in time to see Pheromosa run away, though Rotom only manages to get a blurry photograph of the intruder. Lillie checks on Hala, who then informs the group that his Z-Crystal has been stolen.
The next day, the late-night disturbance has left Ash and his classmates too tired for Pokémon School. Suddenly, Komala rings the school bell, and the Ultra Guardians are called to the underground base for an upcoming mission. They are greeted by Lusamine and Professor Burnet shows the group their data on Pheromosa. Lusamine informs the group that the Ultra Beast appears to be targeting Trainers with Z-Crystals, including Kagetora, Pikala, and Hiroki. Wicke identifies the Ultra Beast as "Pheromosa", and Burnet urges the Ultra Guardians to solve the crisis. To Ash's surprise, the Meltan present the Ultra Guardians with their box of Beast Balls and medical kit. Clefable then rewards the Meltan with some bolts for their assistance. The Ultra Guardians launch out and fly aboard their Ride Pokémon to confront Pheromosa. Meanwhile, at Bewear's den, Pheromosa steals Team Rocket's Darkinium Z and Mimikium Z, but not before Meowth is captivated by its beauty. He decides to refer to Pheromosa as "Beauty" before noticing that it is collecting Z-Crystals.
After seeing the Ultra Guardians flying overhead, Meowth decides to help Pheromosa find more Z-Crystals. Meowth flashes light at the Ultra Guardians with his golden kobana, which gets the group's attention and prompts them to land. They encounter Meowth and become suspicious when he asks them to use their Z-Moves on him. As Ash tries to use his Electrium Z, Pheromosa snatches it off his Z-Power Ring. Ash orders Pikachu to use Quick Attack, but Pheromosa dodges it. Jessie and James soon locate Meowth and notice his drastic appearance changes, including a verbal tic and standing on his toes. Meowth admits that he wishes to impress "Beauty", though Jessie simply wants the Z-Crystals back. James and Wobbuffet find Meowth's affection for the Ultra Beast to be hilarious, but Meowth is too blinded by his crush. He professes his love to Pheromosa, but the Ultra Beast runs off again, and Meowth follows.
The Ultra Guardians return to the base, where Faba reveals his latest invention, the "Sticky Stuck Soles Faba Special". He explains that the wheel on the side will release a gel adhesive around the device, while the Z-Crystal in the bowl will act as a bait. Faba, however, gets stuck in the adhesive. Ash and the others are skeptical, but nevertheless, they set up the device as described in a rocky outcrop and place some Z-Crystals into the dish. Sophocles releases the adhesive before everyone waits in hiding for Pheromosa to arrive. Team Rocket spies on the setup from some nearby bushes and decides to steal the Z-Crystals. Just then, Meowth and Pheromosa stumble onto the trap. Meowth is quick to realize the Z-Crystals are just bait and gets himself stuck in the adhesive. Pheromosa then uses Meowth as a stepping stone and takes all of the Z-Crystals before fleeing the area. Kiawe declares that they will have to face Pheromosa head on. He, Ash, and Lana prepare to attack the Ultra Beast with Turtonator, Lycanroc, and Brionne, respectively.
As the trio charges up their Pokémon with Z-Power, Pheromosa knocks the Pokémon back and swipes three more Z-Crystals. Snowy, Tsareena, and Togedemaru's sneak attack also fails. Jessie orders her Mimikyu to use Shadow Ball, but it instead aims at Pikachu. James has a try, but Pheromosa dodges Mareanie's Spike Cannon as well. Pheromosa rushes towards the trio and overpowers Wobbuffet's Counter attempt. Frustrated at seeing his teammates injured, Meowth manages to free himself of the sticky adhesive and urges Pheromosa to stop attacking them. Pheromosa is unimpressed and kicks Meowth back into the glue pit. Meowth pleads with Pheromosa, but she is despondent. Meowth is left heartbroken, having realized that he was simply being manipulated. Just then, Stufful appears and snuggles up to Team Rocket, after which Bewear appears.
Bewear notices Meowth trapped in the glue and Team Rocket cowering among the rocks, prompting her to confront Pheromosa. The two Fighting types engage in a battle of strengths. Bewear takes Pheromosa by surprise after she knocks it into a cliff. She then corners Pheromosa, though the Ultra Beast is not giving up. Pheromosa attempts to confuse its opponent with its speed, but the tactic fails as Bewear delivers a powerful uppercut. Pheromosa hits the ground and the stolen Z-Crystals fall all around it. Bewear picks up Team Rocket's Z-Crystals, Meowth, and the others before fleeing the scene. As the Ultra Guardians are momentarily perplexed by Bewear's strength, Rotom urges Ash to make the catch, and with Pheromosa knocked out, the Beast Ball successfully captures it. The Ultra Guardians perform their victory pose, although Kiawe is quick to remind them that Bewear is really the one to thank, depressing Ash. Later, Burnet arrives and opens up an Ultra Wormhole with a machine. Ash then calls Pheromosa out. Displeased about being caught, it sticks out its tongue as it returns to Ultra Space. The Ultra Wormhole closes over and Rotom officially declares the Ultra Guardians' mission complete. Ash is relieved, but Sophocles reminds him that they still need to return the Z-Crystals to their rightful owners. Lillie wonders how Faba is doing, and it is revealed that he is still stuck in the adhesive, until Wicke suggests that he take off his clothes. With no other choice, Faba is forced to strip down to his underwear and walk away in embarrassment.
Back at Bewear's den, Meowth is still heartbroken. Bewear arrives with a cache of Berries and shoves a giant Grepa Berry into Meowth's mouth. Jessie and James are quick to remind him that he belongs with them, and the camaraderie begins to cheer up Meowth.