Why did the woman open the door when someone knocked on it?

M: Good morning, madam. I know that you have been robbed.
W: Yes, I have.
M: When did this happen?
W: About two hours ago.
M: Why didn’t you report it before?
W: I couldn’t. I was bound and gagged.
M: Would you like to tell me what happened?
W: Yes, I was sitting in this room watching television when someone knocked on the door. Without thinking, I opened it.
M: That wasn’t very wise, madam.
W: I know. I was expecting my husband, you see, and I thought it was him.
M: You should never open a door without looking to see who it is.
W: Yes, I know. I regret it very much.
M: What happened?
W: Two men pushed me into the flat. One of them threatened me with a knife while the other bound and gagged me.
M: Did you get a good look at them?
W: I am afraid not. They were both wearing stockings over their faces.
M: What did they take?
W: My wallet, which has ＄ 200 in it, my wristwatch, stone of my jewelry from our bedroom, and a silver photo frame.
M: They seem to have done much damage to the flat.
W: No, they had just begun to search when the dogs next door began to bark. They ran off
quickly leaving me bound and gagged. It was some time before my husband returned and released me. I phoned the police at once.
M: The policemen began searching the area as soon as we rceived your call. I can’t promise you that we’ll recover your property but we’ll certainly do our best.