Your step-mom starts out gentle, coaxing you to piss yourself right now. It's ok, just let it go. Let it allll out right now, right where you are. She's soft and nice, and after you've pissed yourself, you realize that she is NOT happy. It was just a test! She's been potty training you, telling you to use the toilet, and she just wanted to see your reaction to being told to piss your pants! You weren't supposed to do it, you failed! You're absolutely disgusting, and she humiliates you for it.