After falling to what appeared to be a Genocidal Human, Sans awakes to a timeline where the child hasn't harmed a soul. However, Sans is quick to learn that this is a timeline where he never existed, and no one knows him-not even Papyrus. Surrounded by familiar faces, he knows their names, and all their little quirks, but to them... He's Just a Stranger.

Frisk and the monsters have finally reached the surface, but it seems something is set on destroying the happy ending permanently. Frisk needs to learn to stand their ground when push comes to shove, and that you can't spare what doesn't want mercy.