There is no double door. Just two single doors. One on the north wall, one to the east.
[sblock=For Strahd]
Zirat again uses his god-blessed ability to detect those of eveil intent, scanning past each door in turn. Through sheer force of will, the mighty paladin block out the background haze of evil, and focuses on details.
To the north, there are no less than a score of evil auras, though they are all but faint, almost invisible against the evil that permeates this place. Whether they are all in the next chamber, or further on beyond that, you cannot be certain.
Behind the door to the east, Zirat detects only four faint evil auras.
[/sblock]