The pills

Sarah was still in the bathroom, but he spotted the pills. He grabbed them and rushed back to his own room. He counted out how many were left. Seven. She must have taken a bunch of them for some reason. That must be why she was acting so weird, they were fake, but not completely, he deduced. They must be an aphrodisiac of some sort. His sister took thirteen, which is why she was so turned on, even by her brother. Maybe they weren't a complete loss.

Would it be immoral to use this to get sex, Adam wondered? Would it even work, his sister took 13, and was still able to turn him away, even if he didn't know what was going on, maybe if he gave them all to someone and tried to seduce them, it would work, but what if it didn't? He could also try giving them to Sarah, with how many she'd already had, it would work, but still, she was his sister. Or he could order more, and try giving all twenty to someone, that could work.