You're on loan to Cassandra from Vivian, so you better be on your best behavior or you're going to get a punishment from both girls! You're to worship her leather ass, grovel at her boots, clean her boots and not do anything you haven't been instructed to do. She knows you'd love to bury your face into her leather-covered ass....but nope, not today.
You obey her commands and get her boots super clean. You get them so clean that she's satisfied and decides to reward you with an offer for you to come upstairs later and drop your load on them.
Behaving pays off!