“There is another possible solution,” said Dick. “Sometimes the people at Chelfordbury avail themselves of a short cut across the park to a neighbouring village.”

“At three o’clock in the morning?”

“There may have been a dance,” suggested Dick lamely.

“A short cut through a park that’s known to be haunted and where a murder was committed two nights ago?”

There was no answer to this.

They reached the bank and followed along the top till they were parallel with the abbey, but there was no sign of man or woman, and they turned back. In spite of his protestations of wakefulness, Sergeant Puttler did not resist the suggestion that he should take his sleep. Dick was left alone to his vigil.

By the time daylight came he was a very weary man. Twice in the night he had visited the two men posted in the corridors above, found them awake, but in each case with nothing to report.

“Thank goodness at any rate somebody’s had some sleep!” he muttered, as he passed under the girls’ window and glanced up.

The morning wind which stirred the trees and filled the world with the pleasant music of rustling leaves moved also the casement window of the room which he had assigned to Mary Wenner. The window swayed to and fro slowly, and he inwardly condemned the girl for not carrying out his instructions.

By six o’clock the first of the servants was stirring; smoke was crawling lazily from one of the big twisted chimneys. He was sitting in envious contemplation of Sergeant Puttler when the door of the study burst violently open and Mary Wenner came in. She was in her dressing gown; her untidy hair floated over her face.

“Mr Alford,” she asked agitatedly, “have you seen Leslie?”

He was on his feet in an instant, and the movement woke the sleeping detective.

“No; she’s with you, isn’t she?”

“We went to bed together,” said the girl, in a tremulous tone, “but when I woke up just now she was not in the room. I waited a while, thinking she was taking her bath, and then I went outside and asked the man you put there. He said she hadn’t come out of the room!”

Puttler, listening, dragged himself erect.

“The ladder!” he said simply, and Dick reeled under the blow.

The Black Terror of Fossaway Manor had in his grip the woman for whom he would have given his soul and counted it no heavy price.