For the Missing Pieces Episode "Room 23", click here.

Room 23 is a room inside a building at the Hydra station. Both Karl and Walt were held at this location. This room is used for brainwashing, which Karl was forced to do. Karl was strapped to a chair, wearing octagon shaped glasses, watching the brainwashing video. In the video, many objects and quotes were seen, including: "Plant a good seed and you will joyfully gather fruit" with a flower. Another quote is "Everything changes". There is a statue of Buddha, and then the moon changing phases. Later, it says "God loves you as He loved Jacob. Sawyer, Kate, and Alex managed to get Karl out and rescue him, but the effects of the video caused him to become unaware of what is happening. Walt was also kept at Room 23. An alarm from Room 23 sounded, and many of the Others are frightened. No one wants to go inside the room. Juliet wants to give Walt back to Michael, but Ben says no, and that Jacob told him to keep him here.