My Duck Is Dead

Trapped in a room with only one door and no windows. Their cell phones do not work and no one outside of the building can hear their calls for help. The group of seven people is under siege as the shape shifting creature tries to seep inside. They are picked off one by one until it is obvious that they cannot out wait this predator. A plan is hatched to retrieve the case that the creature came in to see if it holds any clue to control it or destroy it. When they finally do get the case the creature breaks through the room's barriers and they have to run a macabre gauntlet through the building to the outside world.