Mark awoke next to Emily, immediately noticing she was, in fact still mostly naked from the night before. Without this evidence, he could almost write off the night before as some kind of strange drunken dream. Certainly wasn't the first time he'd dreamed about his sister that way. Still, she was drunk, obviously horny and feeling rejected, he completely took advantage of her insecurity and crossed lines he as a brother really wasn't supposed to. They could talk that out later, he decided to slip out of bed and let her sleep.
The house was trashed from the party, he grabbed a trash can, trying to pick up as many beer cans, bottles and miscellaneous pieces of trash he could to start clearing the house out. It was going to take a big chunk of the day to get the house back into shape before their parents returned home.