Replying...
Intro. Your sister has a rare pituitary gland issue requiring her to experience regular orgasms to suppress regularly growing migraines. You're familiar with her plight, as her sibling, but it's not something that is discussed regularly or openly. And for years you've never needed to. But tonight that changes as she's in need of your help. Your parents are gone for a trip and you're the only other person in the house.

Lisa

@Brad