After rescuing Paula from Happy-Happy Village, you take her back home to Twoson.
Go Back Through Peaceful Rest Valley
Peaceful Rest Valley is still full of monsters, so it may be a struggle to keep Paula alive. Before you leave Happy-Happy Village, you might want to go to Lilliput Steps (or just go partway through the cave) to help level her up.
In Peaceful Rest Valley, go northwest from the cave, then when you see the river, go south along it. Go west across the bridge, then keep going west and cross that bridge (which was broken earlier, but has now been repaired). From there, go south to find the cave back to Twoson.
Reunite Paula with her Parents
In Twoson, go to Polestar Preschool to talk to Paula's mom, then try to go up to Paula's room, and her dad will return. Paula's mom will give you the Hand-Aid, which restores one person's HP completely. You might want to call Escargo Express and have them store the Hand-Aid for later. Just don't forget about it.
Get Cash from Everdred
After you exit the Preschool, a messenger will ask you to go visit Everdred. (If this doesn't happen, go back into the Preschool and talk to both of Paula's parents.) When you visit him, Everdred gives you a wad of bills, worth $10000. This is an item, and it can't be used as actual money, but it will be useful soon.
Watch the Runaway Five
Talk to the guys standing near the bus outside of the Chaos Theater. They give you a Backstage pass to their show. Go into the theater (the Photo Man might appear and take your photo first) and use the Backstage pass to get in. Talk to the girl in the light pink dress to go backstage and talk to the Runaway Five. They need $10000 to get out of their phony contract.
Give Poochyfud the Money
Exit the dressing room and the show will begin. You need to watch the show before you can continue. After the show is over, go back to the lobby, talk to the ticket girl, then go into the office to the left. In the office, stand next to Mr. Poochyfud and use the wad of bills. He will agree to rip up the Runaway Five's phony contract. The Runaway Five rush in to thank you, and they say that they are going to drive to the next town in their bus.
Ride Runaway Five's Bus to Threed
Go outside and the Runaway Five will offer to give you a ride to Threed. This is the only way to get to Threed right now, because if you tried walking through the tunnel, the ghosts would prevent you from reaching Threed.
You will not encounter any random enemies anywhere (in the entire world) while the bus is outside of the theater, so feel free to explore. The ghosts in the tunnel will still send you back to Twoson if you try to go through on foot, though.
When you are ready, talk to Gorgeous (the guy standing outside of the bus), then approach the door of the bus to get on. The loud music will scare away the ghosts in the tunnel to Threed.