The Force Field is an invisible field of energy that surrouds the Cabin, keeping all entities not controlled by the Organisation out, and all of the victims in. Nothing seems to be able to pass directly through the Field, and it appears to have some sort of electrocution effect that kills or disables living things that come into contact with it. It is believed that the Field surrounds the entirety of the area around the cabin, the only portal being the mountain tunnel.
The Field is entirely invisible accept for when in contact with an object. If an object crashes into the field, the field will light up in a glowing hexagonal pattern for a moment before becoming transparent once again.
There seems to be no way to break through the Field and direct contact seems to kill or at least harm living things. The only way through the Field is a small tunnel which runs through a mountain a little ways from the Cabin, which the victims must enter to reach the cabin and is the only way out. Once inside, the victims can leave through the tunnel, but the Organisation collapses the tunnel with explosives to prevent escape.