After someone was covered in it (like Jon and Karyn just were), the slime caused them to absorb the emotions and attitudes of the people around them, to the point where the people contributing the emotions and attitudes no longer had them. And even if Jon and Karyn managed to remove the slime from themselves, the emotions and attitudes that they absorbed would still be part of them ... permanently.
So, just as Karyn was telling Jon about how long it would take her to wash all the slime off herself, she began to feel ...
