The story revolves around the aftermath of a catastrophic event in the Underground. Dr. Gaster's experiment went wrong, and the CORE is overheating, threatening to destroy everything. Gaster and Sans try to minimize the damage, but Gaster is injured and taken to safety by Papyrus and Jessica.
Meanwhile, Undyne fights against a powerful being known as Betty and manages to withstand her attacks. However, Undyne is severely injured and taken to rest.
The story then shifts to Frisk, who is struggling with the consequences of their actions. Frisk reveals to Asriel that they have been lying and pretending to be someone they're not. Frisk has been trying to find a way to reset the timeline but has realized that they can no longer do so. They also reveal that they have been pushing the timeline to its limits and that everything is not going as planned.
Frisk decides to go alone to fight against the being that is hunting for human souls. Asriel is worried about Frisk's safety, but Frisk is determined to continue. The story ends with Frisk's determination to face the challenges ahead, despite the risks.
Here are the key facts extracted from the text:
1. Gaster orders the turbines to be recalibrated and the magnets to be turned off.
2. The CORE's temperature won't go down, and Gaster decides to minimize the damage.
3. Sans tells Gaster to get out of the area as it's falling apart.
4. Gaster says the experiment failed, and the CORE is overheating and will destroy everything if not stopped.
5. Sans tells Gaster to evacuate the area, but Gaster doesn't listen.
6. Undyne fights against Betty and her minions.
7. Betty is surprised by Undyne's determination and strength.
8. Undyne says she's the Spear of Justice and won't back down.
9. Toriel and Asgore argue about bringing Asriel to the school.
10. Asriel wants to go back and help anyone left behind.
11. Frisk tells Asriel that there's no one left to help.
12. A broadcast is sent warning humans and monsters about the pink beings hunting for human souls.
13. Papyrus helps Undyne, who is hurt and tired.
14. Jessica apologizes to Gaster for her role in the death of those close to him.
15. Frisk gives Jessica a gift and tells her to come with him.
16. Asriel talks to Frisk, who says he's been lying and pretending to be someone he's not.
17. Frisk says he's been trying to find a way to reset the timeline since they got to the surface.
18. Asriel is upset that Frisk lied to him and broke his promise not to reset.
19. Frisk says he's been trying every route and variable to get a different ending.
20. Frisk says he's been pushing the timeline to its limits and should have noticed something was wrong.
21. Frisk says he threw the hate from his genocide run onto Chara, which came back blinded by the substance.
22. Frisk says he had the ending he was looking for, but the world continued with him in it.
23. Frisk says he didn't realize he couldn't save or load when he got rid of the reset option.
24. Frisk says it's game over if he loses, and he's the only one who can defeat Chara.
25. Asriel tries to convince Frisk to wait and figure out another way, but Frisk says he's made up his mind to go alone.