With the random movement cross, it's gonna be pretty rare that you're going to have the option of all four directions available to you; there's bound to be a wall in the way somewhere. What happens if you roll, say, a 4, but the direction indicated by 4 leads you into a wall instead of down a hallway? Do you just not get to move?

Answered my own question by looking on the card for "Dust Storm". Wish they'd mentioned that in the rules.