In the climatic finale, Piper Laurie's character takes her mother's portrait off the wall and tosses it. She had been unable to rehearse with the prop (it was their only one) and she didn't realize how heavy it was. When she flung it across the set, it slammed into the camera that was shooting her.
This role was Piper Laurie's "big break." She later learned she'd been recommended for the part by fellow cast member Bob Richards who played her boyfriend. The two had met years earlier in acting classes.