Carl Frederickson had lived a long time, and the majority of his life had been happy. All five of the emotions in his head had learned to work in perfect balance, allowing his time with his wife Ellie to be a good one, through both the good days and the bad. But that all changed when Ellie died. For so long his core memories had been combinations of different emotions, just as all healthy adults have, but suddenly one rolled in that was completely the blue of Sadness. And from that day on, Sadness had taken over the controls.

One by one the islands out the windows crumbled until only Ellie Island was left. Carl's entire life became a drudgery of routine, devoted entirely to living inside his blue-tinted memories of his time with his wife. And while Anger, Fear, and Disgust were allowed their occasional touches, Sadness had long since banished Joy to a circle on the floor. "I know it hurts, but this is what he needs. What else can he do with the little left of his life?"

Joy had accepted the judgment with as much grace as he could muster. After working together for so long, he had to trust the other emotion about his area of expertise. But that changed when Anger spotted Carl's precious mailbox, with its old handprints of his and Ellie's being damaged. For the first time since Ellie's death, Sadness was forced away from the controls as Anger slammed his own levers forward. The result was Carl bashing a man on the head and drawing blood, and before they knew it, he had been labeled a public menace.

This was when Joy decided he had to take action just once more. And as he glanced out the window at the one remaining island, in the shape of Paradise Falls, he knew what he had to do. Seeing that all four other emotions were busy with Carl's complex reactions to his new situation, Joy quietly stepped out of his circle, and grabbed the idea he had first formed long ago, of taking Ellie to see that waterfall they had dreamed of in their childhood. Granted, now that Ellie was gone he didn't quite know what form the idea would take, but it was the one thing he could think to do. So with the bulb in hand, he tiptoed up behind the others, and with lightning quickness inserted it in the controls.

"What do you think you're doing?" demanded Sadness. "I thought you realized you don't belong here anymore!"

Joy drew himself up. "I used to. I don't anymore. I deferred to your judgment, and now it's time for you to listen to mine."

Sadness gave a groan. "Well, there's nothing any of us can do now. That idea isn't coming out. I just hope you don't regret this."

Over the next few days, they watched with fascination as Carl lifted his house off the ground with a countless number of balloons, befriended a boy named Russell, and met a talking dog named Dug and a giant bird named Kevin. Then everything went wrong when they met Carl's childhood hero Charles Muntz. Fear suddenly took over at the signs of several other people who had come across Muntz over the decades and met a dire fate, and after leading them to make an escape, Anger finally shouted, "Move over, it's my turn again!" The result was again disastrous as Carl exploded at Russell and Dug over the trouble they'd caused, and at the devastated look on Dug's face, Anger completely deflated. "I shouldn't have done that. Just like I shouldn't have made him hit that guy. This is all my fault." He walked to the corner and said, "I'm just going to stay here for now. You'll all be better off without me."

Meanwhile, Joy had been placed back in his circle, with Sadness saying "You see what happens when you step in where you don't belong?" Sadness then took his place at the controls back, and brought Carl back to Ellie's book, Stuff I'm Going to Do. He hadn't looked at since that first time she showed it to him, but now Sadness decided this would provide the perfect nostalgic cap to their little misadventure. Then he gasped to discover Ellie had filled the book with photographs of their whole life together, ending with a note thanking him for the adventure. After wrestling with the foreign emotions swirling through him, he walked back over to Joy and said, "I was wrong. About everything. You do still have a place here, and now it's time for you to take it."

Joy leaped up to the controls and filled Carl with the happiness of a life well lived, shining through the sadness that the source of that happiness was gone. A new core memory spilled into the room, once again a mix of yellow and blue. But even that sight couldn't distract Joy from something else that needed to be done; Russell and Kevin were in trouble, and there was only one way they'd be able to help. "Anger, we need you!" he called to where the emotion was still moping in the corner. "Yes, you've made some mistakes recently, but you've also shown that you learned from them. And right now is your chance to make up for it. So what do you say, let's have an adventure together."

Anger jumped up just as enthusiastically as Joy had. "You really mean it?" Joy simply smiled and nodded, and Anger joined him at the controls. Together they filled Carl with the determination to go against his fallen hero, and save all his new friends. And so, Carl began throwing out all he could of the house, though Joy still made sure that his and Ellie's beloved chairs ended up in a respectful position just as they had stood in the house. And as it rose again, all five of his emotions were once again united. Both the immediate future and whatever came next were still up in the air, but they had weathered the bad time and emerged stronger for it. And whatever came next, they would handle it together.