this is really good. smooth, free flowing. you can clearly see the line(s) of movement in the character. I especially like how you kept detail in every little thing; from the door to even the plant in the hallway at the back.
Really nice animation, my only suggestion about your timing. As soon as your character opens the door, i think (s)he reacts too fast that it can be confusing when you first watch it. As soon as the character opens the door, I'd give a good 24-48 frames of him/her just staring, and then reacting. Other than that it's well rendered out and whatnot. :>
If you don't mind me meddling, I don't think the staring part is really that necessary. When people see something they are really afraid of they can react pretty fast, sometimes the brain identify the ''danger'' before the person could have even caught a good sight of it. In case of phobia, people don't really think about what they are doing and just do their best to get away/rid of what is scaring them as fast as they can and can overreact. I know something about it, I've got 1 or 2 phobia myself.
No prob I've got Flash not long ago so I'm learning as much as I can about animation and actionscript myself. One last thing I forgot about the staring thing : though it is not very realistic (except if the person is kinda slow), it can be useful for cartoon/humoristic animation. After all, a person who stare like a moron at something for a few seconds can be pretty funny.