You go South where the old man was and you'll see a red haired guy named Lance. Lance will tell you stuff about the Gyrados being angry and Team Rocket is causing it. You go back to Mahagony town and go into the Souvenir Shop with a sign (the sign says the place isn't suspicous but it is). You'll see Lance beat up a mad scientist. Lance the pushes the geezer blocking the bookcase out of the way and reveals a hidden staircase. The staircase leads to Team Rocket's Headquarters.
Tip: When you first go in, there should be a fork in the hall: one goes straight and one goes down. Take the way that goes down first and battle the scientist and turn off the security cameras. That will make things faster.
Chat with our AI personalities
in johto, go to lake of rage and in the lake is a gyarados [it's red] defeat or capture it and ya'll receive the red scale.
Talk to Mr.Pokemon after you get a red scale from the red gyarados
first you go to lake of rage and catch or defeat the red gyarados and talk to lance at the shore then you go to the house with a tree beside it finish what you have to do there and then go to the gym
it dissapears and you get a red scale but once you beat the elite 4 you get to challenge it
You must be at the Lake of Rage and use Surf to swim towards the Red Gyarados. Either capture or defeat the Gyarados and then make your way back to the bank of the lake, you will now meet up with the black cape guy.