The next morning, he called in sick. Then he walked to the station. Not to take the train—to find the wall.

You left the door open, Mr. Pargeter. You just didn’t know it.

He raised a hand. Just a small, apologetic wave.

He has stopped going to work now. He spends his days walking the tracks, looking for the tunnel. The button has grown warm. Sometimes, when he closes his eyes, he sees the young woman standing in his kitchen, her lichen-dress dripping onto the linoleum, her smile already forming the words:

Saturday he did not work, but he took the 5:47 anyway. He told himself it was for the quiet. The carriage was nearly empty. The door was open now—fully, squarely open, like a mouth mid-yawn. And someone was standing in the doorway.

He found it easily enough. The brickwork was real. The lichen was real. But where the door should have been, there was only a shallow recess, as if something had been carefully removed. And in the recess, pressed into the damp mortar, was a single button. Mother-of-pearl. From a cream-colored dress.

Between Murkwell and Upper Splatt, the train usually passed a long brick wall, blotched with lichen, that enclosed a disused ropeworks. For three years, Mr. Pargeter had looked at that wall. It was the still point of his journey. Tonight, however, a narrow wooden door stood where no door had been before. It was painted a deep, bruised purple, with a brass handle shaped like a sleeping serpent.