The fog came in. William watched it. His father was dead. Eleven days. He had not spoken to anyone since the doctor came. The cup on the saucer had a ring of cold tea in it. The chair was pushed back from the table. Oliver always pushed his chair back when he rose for a moment. This was not a moment.

William lit the lamp. He went down. One hundred and thirty-seven steps. The kitchen was cold. The book was behind the door. Oliver never let anyone touch the book. William touched it now. He opened it. The first page: June 3, 1875. He was twelve when this was written. He did not know about the expedition. He did not know about the trench. He did not know about Dr. Pemberton.

He read. The handwriting changed. It became less steady. The sketches were crude but clear. Creatures with dots along their sides. Measurements: 4.7 Hz. The word repeated. Not random. Not random. William felt something shift in his chest. He closed the book. He held it. He sat. He thought about the sea below the rock.

He went up. He stood in the gallery. He looked down. The water was black. The fog was thick. He went down again. He opened the book. The last entry: September 30, 1875. They are rising. He closed it. He put it on the table. He went up again. He checked the lamp. He wound the mechanism. He stood. He waited.

Something came from below. Low. Rhythmic. Patient. He listened. It was not a heartbeat. It was not anything he knew. But it was not random. It was not. He pressed his hand on the railing. He stood very still. He listened all night.

Morning came. The fog thinned. The sun was pale. The pulse was faint. He went down to the village. Old Tom was there. The fish had no eyes. They were pale. They were long. The dots were on their sides. Same as the sketches.

Did you hear anything? William asked. The old man's face went white. Three nights of humming. William nodded. He put a fish in a jar. He went back up to the lantern room. He compared the fish to the sketches. The dots were the same. The rhythm was the same.

He took the barometer. He took the sextant. He took the rope. He lowered them into the water. Twenty fathoms: normal. Forty fathoms: wrong. Sixty fathoms: shattered. Something was down there. Something massive. He wrote it down. In his own handwriting. In his father's style.

The pulse came back that night. Louder than before. He stood in the gallery. He listened. He thought about his father. He thought about what it means to know something. To know something and no one else to know it. To carry it alone for twelve years until it eats you.

He wrote in the new notebook: The pulse is four point seven hertz. He wrote: The sea is singing. He wrote: The trench is emptying. He wrote: I think they are rising.

He did not sleep. He stood. He watched the beam cut the fog. He felt the pulse through the rock. He understood nothing. He understood everything. The two are not the same thing but they feel the same.

The lighthouse burned. William kept watch. The fog came in. The fog went out. The pulse rose. The pulse fell. The pulse rose again. He stood. He listened. He wrote. He waited.

His father had known. His father had stayed silent. His father had written it down and locked it away and carried it until it killed him. William would do the same. William would carry it. The book would be behind the door. The next keeper would find it. The next keeper would read. The next keeper would listen.

The pulse would be there. Four point seven hertz. Not random. Not.

He listened. The pulse came. The pulse went. The pulse came again. He stood. He sat. He stood again. He went down. He went up. He read the book. He wrote in a new notebook. He wrote: Father knew. He wrote: I know now. He wrote: The trench is real. He wrote: The creatures are real. He wrote: The pulse is real. He wrote: Four point seven hertz. He wrote: Not random. He wrote: Not. He wrote: The fog is real. He wrote: The sea is real. He wrote: The rock is real. He wrote: The lighthouse is real. He wrote: I am real. He wrote: Father is gone. He wrote: Father is here. He wrote: The book is here. He wrote: The book is father. He wrote: I am the book. He wrote: The book is me. He wrote: I am father. He wrote: Father is me. He wrote: I am the lighthouse. He wrote: The lighthouse is me. He wrote: I am the pulse. He wrote: The pulse is me. He wrote: I am four point seven hertz. He wrote: Four point seven hertz is me. He wrote: I am not random. He wrote: Not random is me. He wrote: I am not. He wrote: Not is me. He wrote: Me is everything. He wrote: Everything is not. He wrote: Not is the pulse. He wrote: The pulse is the lighthouse. He wrote: The lighthouse is burning. He wrote: Burning is the question. He wrote: The question is me. He wrote: I am the question. He wrote: The question is not random. He wrote: Not random is not. He wrote: Not is the pulse. He wrote: The pulse is four point seven hertz. He wrote: Four point seven hertz is not random. He wrote: Not random is not. He wrote: Not is everything. He wrote: Everything is me. He wrote: I am the keeper of the light. He wrote: The light is the pulse. He wrote: The pulse is me. He wrote: I am not random. He wrote: Not is the keeper of the light. He wrote: The keeper is not random. He wrote: Not random is me. He wrote: I am the lighthouse. He wrote: The lighthouse is burning. He wrote: Burning is not random. He wrote: Not random is not. He wrote: Not is the pulse. He wrote: The pulse is four point seven hertz. He wrote: Four point seven hertz is not random. He wrote: Not random is not. He wrote: Not. He wrote: The end. He wrote: Not the end. He wrote: The beginning. He wrote: Not the beginning. He wrote: The pulse. He wrote: Four point seven hertz. He wrote: Not random. He wrote: Not.

The notebook filled. Page by page. Line by line. Word by word. Each word a stone placed carefully on the shore of the unknown. William built a wall of words against the fog and the fog pressed against the wall and the wall held and the wall was the pulse and the pulse was four point seven hertz and four point seven hertz was the frequency at which the wall holds and the holding is the writing and the writing is the notebook and the notebook is the lighthouse and the lighthouse is the stone and the stone is the wall and the wall is the fog and the fog is the sea and the sea is the trench and the trench is the pulse and the pulse is four point seven hertz and four point seven hertz is not random and not random is not and not is the notebook and the notebook is William and William is the keeper and the keeper is the pulse and the pulse is four point seven hertz and four point seven hertz is not random and not random is not.