A green spaceship was shown above Earth.
An unknown male voice asked, "Do you think we'll be able to hide here?"
A female voice responded, "We should be able to."
"It's a good thing we got our leader back to the spaceship quickly, that and get away from the authorities." a second male voice said.
A brief flashback is shown of the green ship bumping into a pink ship.
"Now we better hurry." the first one said. "Revenge awaits.
Phineas and Ferb were shown sitting in their backyard with Perry.
Phineas sighed. "Ya know, we haven't done anything since mom and dad left for that Caribbean Cruise yesterday. What are we gonna do today?" He sighed again. "It's too bad Isabella, Buford and Baljeet are in St. Louis without us while their parents are at a big convention of sorts." A communicator vibrated. "What's that buzzing sound?"
Ferb pulled out a communicator and pushed a button, an image of Meap appears wearing a white mustache.
Meap, in English accent said, "Phineas and Ferb. I hate to bother you, but I need your assistance."
"Oh no. Is Mitch up to trouble again?"
"It's not Mitch. It's a group of intergalactic criminals. You probably wouldn't know them."
He pulled up a picture of five aliens.
"Hey, I know those guys! That's Morg and his no good friends!"
"You know of Morg?"
"Morg and his friends tricked me, Ferb, Isabella, Buford and Baljeet into doing a mind swap so that they could be free from their prison." Phineas elaborated. "But I don't get it, how could they have escaped?"
Another flashback of Phineas and his friends in the alien bodies crawling through a large pipe, then putting a picture over the hole. "Oh no..."
"Morg is the leader of the group."
He showed an image of Morg.
"His cellmates are his friends and partners in crime."
He shows another image, this time of an orange reptile in blue striped clothing.
"That's Caro, the right-hand man of Morg and his best friend."
The image then showed another frog alien that was very big.
"Next is Maul, the brains of the gang. He is very smart.
The image changed to a fly.
"Then it's on to Muss. He may look weak, but he's stronger than he appears. He's the muscle of the group."
The image turned into a blue reptile girl with black hair.
"And finally, there's Ezmia. She's sassy, bold and very clever. She's a skilled liar and is said to have a close relationship with Morg."
The image turned back to Meap. "Together, they are the Orange Dragon Gangsters. I need you to tell Isabella, Buford and Baljeet as soon as possible."
"That's going to be hard to do. They're already in St. Louis."
Meap grimaced. "Oh dear. They could be in danger. You have to get over there quickly!"
"Will do." The communicator turned off. "Well, Ferb, I know what we're gonna do today. Hey, where's Perry?"
Perry put on his fedora, entering his lair by filling a bathtub with some water, pulling the plug keeping it in and then flopped onto his chair, soaking wet.
Major Monogram began. "Good morning, Agent P. We've recently noticed that Doofenshmirtz has taken the liberty of going to St. Louis. He didn't bring any of his giant innators with him, but we have reason to suspect that he may be up to something. Get out there and get to the bottom of this! Good luck, Agent P!" Perry saluted him. He took off in his hoverjet. "Carl, where's that coconut milk I ordered?"
"It should be here any minute, sir."
Perry passed by Phineas and Ferb as they made their own space ship.
"Almost done here..."
Candace saw her brothers. "Phineas, what are you up to?"
"We're building a spaceship to meet with Meap in St. Louis."
"Oh you guys are so... Wait, did you say St. Louis?"
Phineas nodded. "Yes. You wanna come?"
Candace answered, "I'm in. Someone has to keep you two boys out of trouble."
She entered the spaceship with Phineas and Ferb, passing Dr. Doofenshmirtz's truck on the interstate.
A chorus sung; "Doofenshmirtz on the road again!"
"Almost there..." he said. "Perry the Platypus! (he presses a button on a remote, a car seat comes up, trapping Perry in leather straps) Ha, now you're trapped! Now I will tell you my plan. Just as soon we get to St. Louis. (cut to Dr. Doofenshmirtz in St. Louis, he stops at a stop sign and takes out a ray gun like device) Behold, the Fall-For-One-inator! With this device I will make a super rich girl fall for me, and get all of her money, and cause another kinds of chaos. (Perry punches Dr. Doofenshmirtz in the face, the truck crashes and the device shots a pink beam, which deflects off of two mirrors, the Gateway Arch, and bounces upwards towards a spaceship, the beam bounces off and destroys several robots, Mitch is seen in the spaceship, looking at a picture of Candace with her brothers, he growls furiously)
Mitch: "That darn Candace Flynn... If it wasn't for her, I would have..." He was hit by the Fall-For-One-inator beam. "have a lovely girl to hold a hand in marriage! Yes, she will be mine!"
He laughed crazily, the scene switched to Baljeet water skiing with Buford driving the boat, where Baljeet nearly loses balance.
"Pay attention up there!" he yelled.
Buford saw the spaceship land. Baljeet lost traction and fell into the water, gasping upon seeing the ship. Isabella looked on in curiosity. Candace, Phineas and Ferb exited the ship.
"Phineas! It's so great to see you!" Isabella cheered. "I thought you wouldn't come."
"Don't get me wrong, I'm happy to see you all again, but unfortunately, I come with bad news." Phineas warned. "Morg and his friends are somewhere in St. Louis."
Baljeet, Buford and Isabella gasped.
Baljeet asked. "Wait, how do you know this?"
"Meap told us that they were hiding in St. Louis." Phineas answered. "He even told us the names of Morg's friends. Caro, Maul, Muss, and Ezmia, who impersonated Ferb, Baljeet, Buford and Isabella respectively."
"And Meap asked us to hunt them down?" Buford raised an eyebrow. "Aren't we a little inexperienced for this?"
Phineas smirked. "Yes, yes we are."
Candace asked, "But what choice do we have?"
Phineas took out the communicator from his pocket, and saw a mustache-less Meap fighting Suzy in the Bango-Ru convention.
"Meap, can you hear me? Meap!"
Suzy jumped onto a giant purple Bango-Ru elephant as a pink animal got destroyed by Meap's rainbow beam.
"They're at the Bango-Ru convention!" Candace told them.
Everyone heard Meap's voice as they saw him flying through the air, landing on top of the St. Louis Gateway Arch.
"Meap!" Meap said, unable to say anything else.
Phineas exclaimed, "We've gotta get him down from there!"
"But how? The arch is very high and..." Baljeet began. Mitch's spaceship appeared and the door opened, revealing Mitch and his robot army. "Uh oh..."
Mitch smirked. "Finally, I found the girl of my dreams! Grab her!"
The robots approached Candace and Isabella.
"Wait a second! Who is Mitch after and why?" Phineas wondered.
Isabella ran towards the edge of the dock to help Baljeet up. The robots grabbed Candace.
She screamed, "Let go of me!"
Buford, Ferb and Isabella fought off the robots.
Phineas yelled, "Candace!" as he was blasted into the water by a beam from Mitch.
Mitch ordered. "Come my robots, we must prepare for the ceremony!"
"W..what?!" Candace asked.
Meap destroyed the robots holding Candace, only for Mitch to grab her and carry her over his shoulder.
Mitch proclaimed, "You'll never stop me, Meap!
He ran into the spaceship, dragging Candace with him. Mitch's spaceship fired a beam at Meap, causing him to fall off the arch.
Isabella and Phineas cried out, "Meap! No!"
Meap screamed his name. "Meap!"
