Sans walks into Dr. Gaster's office and fires a blaster at him. Gaster hires him. The Physics Department, and specifically the Core project, has no budget. Good!Boss Monster!Gaster, Depressed!Sans, Alphys with laser guns, cinnamon roll Papyrus, Grillby the deadpan snark lord, menacing eldritch abominations, souls, EXP morality and mad scientists.