Against Emma's wishes, Nell feverishly questions her about the murder, trying desperately to gain insight into what might have happened to offer a fresh kick to her newspaper, even going so far as to reenact aspects of the murder, in which the father was killed there in the living room. Just as she's questioning Emma about the whereabouts of the murder weapon – the axe – which was never discovered, Lizzy Borden herself appears on the staircase, holding a cat. Stern and contemptuous, she throws the reporter out of the house, calling her bluff for her sister's being naïve in believing that Nell knew their uncle, and sending Emma upstairs. After she is gone, Lizzy goes over to a hidden spot near the fireplace and uncovers the axe. Emma emerges from upstairs and the two have an impassioned discussion in a closed room, in which Lizzy reveals that she's known all along that Emma has committed the murder, because she watched her do it.
Emma explains how much she hated their step-mother, and how she had even turned her father against them. Then Emma asks why Lizzy endured all the prosecution, and never ratted on her. Lizzy says that Emma is her sister, and that she loves her. But then Lizzy thinks of all her days being scorned and ridiculed by the press and by the public, and wonders what Emma would have done if she had been convicted. She realizes that Emma would have allowed her to go to prison for the crime. As the two talk, Lizzy realizes how very unstable Emma is, and while Emma yet has the axe in her hands, Lizzy tries to convince her to go see a doctor that they know. Emma refuses, horrified by the idea of being put away somewhere. Emma is about to turn on her sister with the axe, knowing that she's the only one who knows of her guilt, when the doorbell rings. It's Nell again, and in the process of trying to get a statement from her, Nell sees the axe lying there. As Emma rushes out the door to catch her train, Lizzy tries to do damage control. But the reporter realizes that it wasn't Lizzy after all. Through the window, Lizzy watches as Emma bids farewell to a neighbor, informing her that she's not leaving for vacation, but for good, and that she'll never return to that house again.
With Nell gone, Lizzy is left all alone in the big old house, with even the maid too terrified to stay with her. The scene fades out with her holding her cat, sitting all by herself in the living room