Palace of the Angels

From the introduction:

The Tardis lands and the time lord and his companions head outside. They seem to be in a darkened room as they look around it turns out to be an 19th century room full with furniture and art. There is a faint sound of music coming from behind a double set of doors, as they come closer they also hear the sound of laughter and speech. As they open the doors it turns out that there is an 19th century party going on, or is it a costumed ball?