The Royal Scientist was shattered across space and time, never to be seen again... but the three broken pieces of his soul didn't die with him. Instead, each found a place in a human child. Exactly seventeen years later, the trio are drawn back into the Underground to finish a plan they set in motion long ago, in a life they never lived.

Three years after the events of Undertale, Frisk has settled down with their family. All is peaceful, until some unknown force revives an old adversary. Taking renewed control over Frisk's body, Chara has finally returned. Will Frisk be able to defend their family from Chara's revenge? Or will they fail, and leave the world to destruction?