The morning alarm sounds, waking Pikachu up from his sleep, but Ash remains asleep. As Pikachu walks over to turn the alarm off, Ash grabs the Poké Ball-shaped device and throws it at the wall in his sleep. With the alarm clock broken, Pikachu resorts to zapping Ash to get him up, but this also fails. Soon, Delia enters the room and reminds her son that he needs to get off to Professor Oak's Laboratory. Ash finally wakes up in a state of panic before he and Pikachu rush off to the Lab.
Ash and Pikachu arrive at the lab, where they greet Professor Oak just as he is packing his car. Oak reveals that a new Professor is opening a lab in Vermilion City, and invites Ash to attend the opening ceremony. Ash enthusiastically agrees to come along, as does Delia and Mimey. Delia admits she is looking forward to doing some shopping in Vermilion, much to Ash's disappointment. During the cross-country road trip, Ash is thrilled to see all the wild Pokémon and is determined as ever to become a Pokémon Master alongside Pikachu.
Oak pulls up in front of the Cerise Laboratory, dropping off Ash and Delia while he looks for a parking spot. Eager to have a look around, Ash rushes up the fleet of steps only to be stopped by a yapping Yamper. Ash, however, is overcome by the Electric puppy's cuteness and tries to pat it. He eventually catches it, only to receive an electric shock for his efforts. Yamper then spots Pikachu and instantly takes a liking to him. After a day at school, Chloe stumbles upon the scene and simply walks around Ash to continue home. Professor Oak soon notices Ash sprawled on the ground and orders him to get up for the opening ceremony.
Inside the Cerise Laboratory, Professor Cerise, with his two assistants, Chrysa and Ren, as well as Professor Oak on stage, welcomes the gathered press to his laboratory. Cerise explains that his Institute aims to understand everything about Pokémon to better understand the world. Meanwhile, Chloe is waiting patiently upstairs for her friend Goh to arrive for the opening ceremony. She is left unimpressed after she receives a text message from Goh explaining that he will be late as he is waiting for a fateful encounter.
Atop a building rooftop, Goh analyses the weather conditions as he awaits his fateful encounter. Similarly, Cerise receives an alert, and after some analysis of the humidity and wind speeds, he deduces that a rare Pokémon will arrive at the Vermilion Harbor in 20 minutes. Ash rushes off to investigate further, and much of the crowd follows, suspecting it might be a Legendary Pokémon. Suddenly, a swirling dark cloud appears over the harbor and a Lugia roars into view. Other expectant Trainers call on their Pokémon to take on the Legendary in a Raid Battle, but Lugia's power easily takes out all of its opponents. Lugia lands by a pier to rest momentarily, though its break is interrupted by a battle challenge from Ash. Pikachu leaps into action, launching a Thunderbolt. Lugia shakes the attack off and replies with a flash of Aeroblast before flying off.
Ash and Goh remain determined, both leaping from ledges to land on Lugia. Goh grabs a hold of Lugia's tail, while Ash and Pikachu struggle to hold onto one of Lugia's legs. Surprised at first, the two Trainers resort to helping each other onto Lugia's back. Lugia, however, doesn't seem to mind having passengers. Goh takes the opportunity to record Lugia's flapping fins and glimmering silver feathers on his Rotom Phone. Abruptly, Lugia flies up even higher to join a flock of passing Fearow. As Ash and Goh admire the altitude, Lugia descends suddenly towards the ocean. The boys shriek as they anticipate the hard landing, but Lugia uses Hydro Pump to blast a hole into the water surface. Lugia soars through the wall of water and into the oceanic depths, teeming with Water Pokémon. A school of Horsea take the boys by surprise, almost causing Ash and Goh to run out of air. Luckily, Lugia emerges from the water and take to the sky once again. Goh is pleasantly surprised as Ash marvels over the wonders of Pokémon. Goh formally introduces himself, revealing he is from Vermilion City, and declares that he and Ash are now friends. Ash follows suit, introducing himself and Pikachu. Suddenly, Lugia tips its passengers off, and they land in a field of flowers. Lugia promptly leaves while Goh and Ash wave the Legendary goodbye. The pair enjoy the moment, but then realize they don't know where they are or how to get back to Vermilion.
By evening, the two boys finally arrive back at the Cerise Laboratory. There, Yamper enthusiastically greets Pikachu. Chloe, however, is still disappointed that Goh failed to make it to the opening ceremony. She dismisses his Lugia encounter story and presents Goh with a handful of school worksheets. Goh quickly perks after Chloe admits her father, Professor Cerise, is talking with Professor Oak. Inside, Cerise is thrilled by Goh's closeup footage of Lugia. Ash reveals that Lugia took a liking to them, and Goh soon comes to the same conclusion as well. Cerise is impressed by the boys' insights and proposes they become research fellows at his lab. Ash doesn't quite understand, so Cerise elaborates that he wants them to meet Pokémon. Goh accepts the honor, while Ash is excited by the future ahead. Delia reminds her son that commuting between Pallet Town and Vermilion City will be tough. At this, Professor Cerise presents the boys with their very own dorm room. The solution is a hit as the two boys squabble for the top bunk. Delia also decides that Mimey should also stay at the Cerise Laboratory to keep Ash out of trouble. As Delia and Oak prepare to drive back to Pallet Town, Delia tells her son to eat his vegetables and brush his teeth, to which Ash embarrassedly accepts. Delia also asks Goh to look out for Ash, much to his embarrassment, before leaving with Professor Oak.
Chloe reminds her father that he forgot something. Cerise takes a moment to prepare before revealing the three starter Pokémon on offer at his lab: the Fire Pokémon Charmander, Grass-type Bulbasaur and Water-type Squirtle. Cerise prompts Goh to make his selection. Goh declares that his first choice is the Mythical Pokémon Mew. Cerise is left baffled, but Goh insists that Mew is perfect for him. He shows a photograph of his first encounter with Mew, and the long-awaited ambition spurs Ash to cheer him onto success, while Chloe is left dumbfounded by the statement. Professor Cerise laughs and offers his encouragement to Goh and Ash towards their goal of uncovering the secrets of Mew.