From The Grey House:
Vincent left the room, and the memories, behind. It was called an oubliette for a reason.
Rebecca closed and locked the door once he was out. Joseph followed behind him as he walked up the passage to the cellar steps. Mierka and two others were waiting for them by the door. As they approached, one went into the air chamber. By the time Vincent reached the door, it was open. Mierka was standing by it, waiting. Vincent stepped through, closed the door then opened the other. His thoughts were far from pleasant as he walked up the steps.