The story begins a few minutes after the destruction of the Barrier. Toriel and the Antagonist, then head down the mountain of which the Monster were trapped under. Then the player meets their friends at the bottom of this mountain. Asgore asks the Player if they are ready to introduce them to the Humans, of which we are not given the choice to reply to and Asgore's response is if we were to say "Yes". Sans, then, says "Let's hope they like us." before going on to say that it might help if he told the Humans some of his jokes, of which Asgore says that they should keep their jokes to themselves before saying that it's time to enter the nearby village. The screen, then, fades to black.
The story continues after a couple of months. The player wakes up in the bedroom of their home. Coming out of the bedroom and going to the first floor, they meet Toriel, who says that you to go for a walk. Next, the player must leave the house. They can see the homes of other Monsters, as well as a bar called "Grillbys". Then, the player needs to go upwards where you can see the House of Papyrus and Sans. On the door is a note from Sans and in which he says that we should go to his laboratory. Next, it shows a warning that you can not go back.
If you go Away, the player will see Ihe, who will show him the time machine allows you to travel in the other timelines. Further, he will talk about Memes and that the latter wanted to see what would happen if you kill some creatures in the other timelines. Then Gaster wanted to make a Genocide in some timelines. Next, we show a scene in which Sans tried to persuade him not to do it, but Gaster still activated the machine. Sans used his attack and destroyed the Time Machine. Then he says that because of this Gaster got stuck in "The Void". Sans tries to repair the time machine. Then he tries to turn it on, and the screen turns white.
The player enters the distorted emoji Movie. Sans calls you and says that he got a Pewdiepie pet on club pengy of the Snowdin as well. Later, you can find a variety of puzzles. There is also buggy monsters in the Ruins. When you pass the Ruins, you go to Snowdin. Sans calls the player and says that he was in Waterfall. In Snowdin you also meet buggy monsters, among which is Jerry, which does not attack, as well as in the canon. Once you get into Snowdin Falls. In it, you can see the silhouette, of Gaster. In the next room, the player calls Sans and says that he's already in Gaster's Lab. In Waterfall there are no puzzles and enemies, but there are signs that tell about the history of Gaster.
Then the player enters Jerry's Lab. Later you will see that the door to the Fake Laboratory opened. But there's just a black corridor instead of the True Lab as before the battle with Omega (Photoshop) Flowey. At the end, there is a door to the room where Gaster is located. It is when he tries to take your soul from you. Yet, when interacting with it, the beta ends.