The butlers give a simultaneous jerk on the cords, just as you are realizing exactly what is going on, but by that moment, of course, it's far too late.
The timing of the cord pull was not a coincidence, and the whole room is bathed in the light of the full moon directly overhead, shining through the skylight.
All around you, the guests begin to make primal, bestial, gutteral sounds, tearing at their clothes. Your hostess is no exception, her body swelling with muscle mass, and her beauty being torn away by a newly emerging bestial visage.
The guests begin to howl, their faces stretching into muzzles, their teeth to fangs, and their nails to talons. Your hostess now turns to you, sinking her fangs into your hand, which you carelessly left within reach.