Six months after the murdering, Audrey Jensen decides to take a break from Lakewood, and instead go hiking on a mountain. But when things don't go as planned, Audrey finds herself in the Underground. Now, she must find a way out of the Underground, along with making new friends, and meeting new foes. Will she escape, or die trying?

After completing a true pacifist route, Asriel, who has a soul thanks to Frisk, finds out he can create links to other timelines. But when Chara creates a time link into the real world, it's up to Asriel, Sans, Miguel, Alphys and Undyne to stop Chara from killing everyone in the real world, and to restore it.