Back inside Hope's End, Kit finds Mrs. Baker and Jessie rattled by the commotion outside. Mrs. Baker dismisses the intruders as trespassers, and Kit supports the story, telling Jessie it was just kids fooling around. Even after the danger passes, Kenny's warning stays with Kit and pushes her to reconsider Mary Milton's death.

As Kit thinks through the evidence, she sees a possible explanation for Mary's murder: Lenora may have regretted sharing too much or may have tried to stop Mary from exposing the truth about the blood test. Kit also revisits the bruise on Lenora's arm and the possibility that Mary drew blood from Lenora by force. Those thoughts lead Kit to an even more disturbing theory: Lenora may not be as helpless as she appears.

Kit connects that suspicion to other unsettling incidents at the house, including the Walkman turning off, the noises from Lenora's room at night, the shadow at the adjoining door, and the blur at the window. When Kit checks on Lenora, Lenora appears asleep, but Kit no longer trusts appearances. She decides the only way to know whether Lenora is faking paralysis, muteness, or both is to catch her doing something she should not be able to do.

To test that theory, Kit props open the adjoining door between their rooms, changes clothes, and settles into bed with a book and a thermos of cold coffee so she can stay awake. She keeps the doorway in view for hours, reading, listening to the waves, and forcing herself to remain alert. Eventually, however, exhaustion overtakes her.

Kit jolts awake from a nightmare about her dead mother and realizes the sound pulling her from sleep is Lenora's alarm. The adjoining door, which Kit left open, is now shut. She rushes into Lenora's room and finds Lenora awake and terrified, holding down the call button while staring at the typewriter. A fresh page in the carriage repeats the sentence It's all your fault over and over. When Kit asks if Lenora's sister did it, Lenora taps twice, confirming yes.