* After falling in the Underground, the young human Frisk encounters the Monster race living there, after having been magically locked in the cavern by the Humans, a thousand years ago.

* Through a eventful adventure, Frisk befriended the prisoners and managed to break the magic barrier preventing everyone to leave the Underworld. But upon opening the Great door to free them, the latter remained closed, for unknown reasons.

* It is now up to Frisk to understand what happened.

* But the world is shifting. The rules are changing. Without them knowing it, a greater design is already in motion, to change the face of the Underground.

* You are facing the beginning of a new era. Will you be able to stop it. Will you help it to happen? What will your choices create? What will they destroy?

* Shall we discover it?