“That was our first idea.  But see!” Barker drew aside the curtain, and showed that the long, diamond-paned window was open to its full extent.  “And look at this!” He held the lamp down and illuminated a smudge of blood like the mark of a boot-sole upon the wooden sill.  “Someone has stood there in getting out.”

“You mean that someone waded across the moat?”

“Exactly!”

“Then if you were in the room within half a minute of the crime, he must have been in the water at that very moment.”

“I have not a doubt of it.  I wish to heaven that I had rushed to the window!  But the curtain screened it, as you can see, and so it never occurred to me.  Then I heard the step of Mrs. Douglas, and I could not let her enter the room.  It would have been too horrible.”

“Horrible enough!” said the doctor, looking at the shattered head and the terrible marks which surrounded it.  “I’ve never seen such injuries since the Birlstone railway smash.”

“But, I say,” remarked the police sergeant, whose slow, bucolic common sense was still pondering the open window.  “It’s all very well your saying that a man escaped by wading this moat, but what I ask you is, how did he ever get into the house at all if the bridge was up?”

“Ah, that’s the question,” said Barker.

“At what o’clock was it raised?”

“It was nearly six o’clock,” said Ames, the butler.

“I’ve heard,” said the sergeant, “that it was usually raised at sunset.  That would be nearer half-past four than six at this time of year.”

“Mrs. Douglas had visitors to tea,” said Ames.  “I couldn’t raise it until they went.  Then I wound it up myself.”

“Then it comes to this,” said the sergeant:  “If anyone came from outside—­if they did—­they must have got in across the bridge before six and been in hiding ever since, until Mr. Douglas came into the room after eleven.”

“That is so!  Mr. Douglas went round the house every night the last thing before he turned in to see that the lights were right.  That brought him in here.  The man was waiting and shot him.  Then he got away through the window and left his gun behind him.  That’s how I read it; for nothing else will fit the facts.”

The sergeant picked up a card which lay beside the dead man on the floor.  The initials V.V. and under them the number 341 were rudely scrawled in ink upon it.

“What’s this?” he asked, holding it up.

Barker looked at it with curiosity.  “I never noticed it before,” he said.  “The murderer must have left it behind him.”

“V.V.—­341.  I can make no sense of that.”

The sergeant kept turning it over in his big fingers.  “What’s V.V.?  Somebody’s initials, maybe.  What have you got there, Dr. Wood?”

It was a good-sized hammer which had been lying on the rug in front of the fireplace—­a substantial, workmanlike hammer.  Cecil Barker pointed to a box of brass-headed nails upon the mantelpiece.