As it suggests in the Scenario Book, as a marine player opens any door I pause the game and lay out the newly-discovered area, placing all monsters / items etc etc for that area.
Now let me throw a scenario at you to help better understand my situation:
Our lone Marine is standing in a T-junction, with his back to the (closed) door he just came through. The Invading player plays a spawn card, however is unable to place the creatures anywhere along the T corridor as there are no "blind spots".. so places them behind the door, in the room the Marine was previously in as they are not in line of sight (due to the closed door).
Which option would you favour:
1) I state I'm playing a spawn card, and grab the miniatures from the box. Place them on the board for the player to see, behind the door.
2) I state I'm playing the spawn card... and don't put anything on the board as technically the Marine can't see the figures.
Now, we're trudging I think between "board game" and "realism". With option 2) the player knows there are more invaders around.. but no idea where. Spooky huh? However with option 1) it can lead to a "obviously we won't backtrack that way" or "look, the invaders are taking the another way around".
How do "you" deal with this situation?