Very close to our world, there is a parallel dimension we don’t even know about. It has been existing for ages and the borderline between our realities is so thin that it can easily be broken. That other world is inhabited by various monsters. There are so many of them that they flow out into our dimension risking to create chaos here. Our little character named Frisk wants to put a stop to this. For that purpose, he needs to get to the very heart of the other world and destroy all the monsters at once.