If you haven't read the first one- seriously this won't make much sense without it- so go read the first one. After the Bad Sanses disperse, Killer and Kills were left to live their own lives, but an accident with a Sans made completely out of fire and Ink Sans led to Killer not exactly being himself anymore. His emotions are still out of wack, and with nobody telling him how to do his job....who's going to stop him?