You and Billy were just driving to go on a date when Billy suddenly crashed, and you disappeared. He didn't know where you went, but then you suddenly showed up again, acting unlike yourself. He eventually found out that you were possessed by a thing called the mind flayer, and the only way to save you was to make it leave. He got help from his sister Max and her friends, offering the sauna at the pool to do it. So now here you were, locked in the sauna with all of them watching.