- Cut to the morning. Joy's still dragging Sadness. She's exhausted, and they don't seem to be getting any closer.
- They stumble across some Mind Workers vacuuming faded memories that they don't think Riley needs anymore from the Long-Term Memory shelves—memories like most of what she learned at piano lessons and all the presidents except for Washington, Lincoln, and "the fat one."
- Joy insists that all memories are important. The Mind Workers disagree, and explain that when Riley doesn't care about a memory, it fades. The faded ones end up in the Memory Dump, and nothing ever comes back from the Memory Dump.
- Never? Does anybody else smell foreshadowing?
- Riley video-chats with her BFF Meg back in Minnesota. Meg tells her that they have a new girl on their hockey team, and she's, like, so cool. Riley gets upset and ends the chat.
- Friendship Island bites the dust, crumbling into the Memory Dump. Joy watches it disappear in disbelief, but remains resolved to return to HQ. She grabs Sadness by the ankle and gets ready to resume their trek when she spots an unfamiliar creature picking over the memories on a shelf ahead.
- He looks like a pink elephant dressed as an old timey clown. Once he sees Joy, he takes off running.
- Joy catches him and, what's this? She recognizes him. He's Bing Bong, Riley's imaginary friend. She hasn't seen him in ages.
- Joy seems a bit star-struck. Bing Bong does, too, on account of the whole "without Joy, Riley will never be happy again" thing.
- Bing Bong explains that he's just been bopping around out here in Riley's brain all this time, and offers to help Joy get back to HQ.
- He also explains that he is part elephant. He's also part cat and part dolphin, but he's mainly cotton candy.
- He also has a bag that, since it's imaginary, can hold as much as you can possibly shove in it. That comes in super-handy for toting the Core Memories back to Headquarters.
- Joy's grateful for Bing Bong's help, and says that when she does get back, she'll make sure Riley remembers Bing Bong.
- Bing Bong cries tears of joy, except he doesn't cry tears, he cries candy.
- According to Bing Bong, they can catch the Train of Thought in Imagination Land, and he knows a shortcut to get there.
- Turns out the shortcut is through Abstract Thought. Sadness tells Joy that they shouldn't go through there; the manual said so. Joy can't pass up a juicy shortcut, though, and Joy and Sadness follow Bing Bong into Abstract Thought.
- Cut to Riley eating lunch by herself at school.
- Two Mind Workers approach the entrance to Abstract Thought that Bing Bong, Joy, and Sadness just went through—the one clearly marked DANGER—and discuss how today they're going to be working on the abstract thought of loneliness. First, though, they should burn the gunk out.
- As Bing Bong, Joy, and Sadness walk through the darkened corridor of Abstract Thought, suddenly the lights come on. They're in a large, white room—or maybe it isn't even a room; maybe it's just space—and surrounded by colorful, floating, 3-D shapes.
- Suddenly Joy, Bing Bong, and Sadness all turn into weird collections of 3-D shapes themselves. They look like a trio of Picasso paintings. Sadness says they're going through the first stage of abstract thought: non-objective fragmentation.
- Next, they all fall apart. That's stage two: deconstruction.
- As the train beckons in the distance, they hit stage three and become two-dimensional. That's not going to help them get to the train any faster—or get out of there, period. Sadness says they could end up stuck in there forever.
- As the train idles outside, they reach the exit, but in their flattened state, they can't fit. Then stage four hits: they're non-figurative, which means they're just colored blobs.
- Sadness realizes that they're still 2-D and tells Joy and Bing Bong to fall on their faces. They do, and they shimmy out the door—just as the train pulls away.
- They cycle back through the abstraction stages to their normal selves, and Bing Bong says not to worry: The Train of Thought makes one more stop before it returns to headquarters, and he knows a shortcut to there, too.
- Why Joy and Sadness decide to follow him on another one of his shortcuts is beyond us, but hey, desperate times, desperate measures and all that, right?