Just to clarify the nature of that excellent demo shown to the public back at Leipzig, Heavy Rain producer David Cage has stated that the chosen scene definitely doesn't form a part of the core plot.
“It’s really a bonus scene,” stated the developer. “It will probably be on the game disc.”
Likely to form the basis of a tutorial, the level in question saw our investigative player breaking into a spooky house before being chased by a knife-wielding resident amidst rooms full of corpses and mannequins.
The game itself is made up of over 60+ scenes, all of which will contain multiple endings depending on the approach used. Choose-your-own adventure game, essentially.
In fact, why not take a look yourself.