From Glitchtale Wiki
While unconscious, Gaster recalls an old memory of himself, Sans, and another person operating within the CORE. An accident causes Gaster to fall into the depths of the facility, leading to his appearance in The Void. Gaster soon wakes up to find himself in Papyrus' and Jessica's care. When he is told of the situation, he believes that they need to assist Undyne. However, he discovers that he’s bleeding. Because Monsters are normally composed entirely of magic, they shouldn’t be capable of bleeding. He then concludes from this that Undyne has the potential to defeat Betty.
Bete Noire prepares for battle within The Nullifier Room, believing that Undyne will fall as the other Monsters have. However, to her surprise, Undyne outclasses her in every regard thanks to her empowered state. Bete Noire barely manages to avoid fatal damage, and any attempts to attack or defend are met with overwhelming strength. Undyne's wounds heal before any real damage can be dealt. Even Rhabdophobia is useless against Undyne, as no matter how many of her spears are taken, she can effortlessly make many more. All the while, Betty is unable to comprehend how Undyne can possess Determination, as Monsters should be unable to.
Before their fight can escalate any further, Bete Noire is able to regain control of her body, but sees that HATE carries risks and decides to retreat with Akumu. Rather than pursuing, Undyne falls to the ground and reverts to her normal form. She then weeps over the death of Alphys.
The Bete Noire has taken refuge in an unknown, decrepit wooden shed. Here, she discusses with Akumu that consuming HATE all at once has led to her losing control over her own body. She's afraid of the substance and what might happen if it's able to take over completely. After this, many pink blobs return from their assault on the school. Akumu them consumes the creatures and claims the collected souls for itself and Bete Noire.
Frisk appears somber and demoralized after the many deaths he had seemingly failed to prevent. This is only made worse after he discovers that Alphys had been killed. His personality has shifted drastically, and he has become more quiet and passive-aggressive than ever before.
This part begins with Papyrus looking at the stars, Undyne resting in bed, and Asgore watering flowers. Toriel prepares a sandwich, and Jessica caresses a set of ballet shoes that Frisk gave her, which previously belonged to her own daughter.
Frisk experiences flashbacks of the fights he took part in. Toriel interrupts him and offers him food. However, Frisk rejects the offer and is rude to Toriel. Meanwhile, Jessica talks to Ronan Cass, a police chief, through the phone about a magical barrier deployed around the city.
At a similar time, Gaster reviews footage recorded at the time of the barrier being broken. He discovers that the AMD had captured a then-unknown entity and put it in storage. He also discovers that Jessica had been aware of this same entity since it was captured. He then questions Undyne in front of both Jessica and Papyrus, and confirms that the substance was HATE itself. He is furious that Jessica had not informed him about it and berates her before leaving. This strips Jessica of her trait once more.
Asriel finds himself conversing with a mental recreation of Flowey. Here, Flowey mocks Asriel's current predicament and encourages him to be more cold-hearted like he used to be. However, Asriel chooses to accept both his past and present, and move towards the future. Then, with a locket in hand, he leaves the house to find Frisk and lend his aid.
Through a telepathic link, Gaster and Papyrus are both alerted that Sans is once again alive. Despite Gaster's pleas, Papyrus runs off to find Sans. Toriel notices Asriel is missing before she, Asgore, and Gaster depart for the battlefield as well.
Frisk struggles to defeat the Bete Noire while Sans is present, but before Sans can finish the fight with a Gaster blaster, Papyrus intervenes. As Asgore, Toriel, and Gaster arrive, Bete Noire creates a dome that seals the four of them off from the outside world. Here, Papyrus attempts to pacify Sans through words rather than violence, while Frisk engages Bete Noire once more. After a short amount of time, Papyrus is able to free Sans from his current circumstances, and the dome is destroyed. Bete Noire manages to escape while everyone turns their attention to the now-unconscious Sans. Frisk asks Papyrus how he has managed to continue to act as he always has, and Papyrus' answer leads to him devising a way to rescue Asriel using the power of love.
- It wasn’t until the release of Game Over Part 1, over 10 months later, that the reason for several things in this episode were explained. When Asriel is falling asleep, the negative frame indicates the exact moment Chara entered the timeline from Game Over. The locket in the mirror (that wasn’t there before) and the blanket on Asriel, after he wakes up, are also Chara’s doing.