Complex sentence: She sees a shadow out in the hall and hides in her closet, it is Fenton, but the person is only Winn and Fenton grabs Donna in the closet.
Split into simpler sentences: She sees a shadow out in the hall and she hides in her closet, thinking the shadow is Fenton's. The person in the hall is Winn and Fenton grabs Donna in the closet.