As there were no screens, the windows had not been raised.

A big fly was buzzing angrily at one of them now, up and down, up and down, trying to get out.
Miss Polly killed the fly, swept it through the window (raising the sash an inch for the purpose), straightened a chair, frowned again, and left the room.
"Nancy," she said a few minutes later, at the kitchen door, "I found a fly up-stairs in Miss Pollyanna's room.

The window must have been raised at some time.

I have ordered screens, but until they come I shall expect you to see that the windows remain closed.

My niece will arrive to-morrow at four o'clock.