“Quite so. It doesn’t prove it wasn’t used. But there might havebeen stains， and that would have helped us. As a matter of factthere were none. Then I examined the gun. They were buckshotcartridges， and， as Sergeant Wilson pointed out， the triggers werewired together so that， if you pulled on the hinder one， bothbarrels were discharged. Whoever fixed that up had made up hismind that he was going to take no chances of missing his man. Thesawed gun was not more than two foot long—one could carry iteasily under one’s coat. There was no complete maker’s name； butthe printed letters P-E-N were on the fluting between the barrels，and the rest of the name had been cut off by the saw.”
“A big P with a flourish above it， E and N smaller？” asked Holmes.
“Exactly.”
“Pennsylvania Small Arms Company—well-known Americanfirm，” said Holmes.
White Mason gazed at my friend as the little village practitionerlooks at the Harley Street specialist who by a word can solve thedifficulties that perplex him.
“That is very helpful， Mr. Holmes. No doubt you are right.
Wonderful！ Wonderful！ Do you carry the names of all the gunmakers in the world in your memory？”
Holmes dismissed the subject with a wave.
“No doubt it is an American shotgun，” White Mason continued.
“I seem to have read that a sawed-off shotgun is a weapon usedin some parts of America. Apart from the name upon the barrel，the idea had occurred to me. There is some evidence then， thatthis man who entered the house and killed its master was anAmerican.”
MacDonald shook his head. “Man， you are surely travellingoverfast，” said he. “I have heard no evidence yet that any strangerwas ever in the house at all.”
“The open window， the blood on the sill， the queer card， themarks of boots in the corner， the gun！”
“Nothing there that could not have been arranged. Mr. Douglaswas an American， or had lived long in America. So had Mr. Barker.
You don’t need to import an American from outside in order toaccount for American doings.”
“Ames， the butler—”
“What about him？ Is he reliable？”
“Ten years with Sir Charles Chandos—as solid as a rock. He hasbeen with Douglas ever since he took the Manor House five yearsago. He has never seen a gun of this sort in the house.”
“The gun was made to conceal. That’s why the barrels weresawed. It would fit into any box. How could he swear there was nosuch gun in the house？”
“Well， anyhow， he had never seen one.”
MacDonald shook his obstinate Scotch head. “I’m not convincedyet that there was ever anyone in the house，” said he. “I’m askingyou to conseedar” （his accent became more Aberdonian as he losthimself in his argument） “I’m asking you to conseedar what itinvolves if you suppose that this gun was ever brought into the house，and that all these strange things were done by a person from outside.
Oh， man， it’s just inconceivable！ It’s clean against common sense！ Iput it to you， Mr. Holmes， judging it by what we have heard.”
“Well， state your case， Mr. Mac，” said Holmes in his mostjudicial style.
“The man is not a burglar， supposing that he ever existed. Thering business and the card point to premeditated murder for someprivate reason. Very good. Here is a man who slips into a housewith the deliberate intention of committing murder. He knows，if he knows anything， that he will have a deeficulty in makinghis escape， as the house is surrounded with water. What weaponwould he choose？ You would say the most silent in the world.
Then he could hope when the deed was done to slip quickly fromthe window， to wade the moat， and to get away at his leisure.
That’s understandable. But is it understandable that he should goout of his way to bring with him the most noisy weapon he couldselect， knowing well that it will fetch every human being in thehouse to the spot as quick as they can run， and that it is all oddsthat he will be seen before he can get across the moat？ Is thatcredible， Mr. Holmes？”
“Well， you put the case strongly，” my friend replied thoughtfully.
“It certainly needs a good deal of justification. May I ask， Mr.
White Mason， whether you examined the farther side of the moatat once to see if there were any signs of the man having climbedout from the water？”
“There were no signs， Mr. Holmes. But it is a stone ledge， andone could hardly expect them.”
“No tracks or marks？”
“None.”
“Ha！ Would there be any objection， Mr. White Mason， to ourgoing down to the house at once？ There may possibly be somesmall point which might be suggestive.”
“I was going to propose it， Mr. Holmes； but I thought it wellto put you in touch with all the facts before we go. I suppose ifanything should strike you—” White Mason looked doubtfully atthe amateur.
“I have worked with Mr. Holmes before，” said InspectorMacDonald. “He plays the game.”
“My own idea of the game， at any rate，” said Holmes， with asmile. “I go into a case to help the ends of justice and the work ofthe police. If I have ever separated myself from the official force，it is because they have first separated themselves from me. I haveno wish ever to score at their expense. At the same time， Mr.
White Mason， I claim the right to work in my own way and givemy results at my own time—complete rather than in stages.”
“I am sure we are honoured by your presence and to showyou all we know，” said White Mason cordially. “Come along， Dr.
Watson， and when the time comes we’ll all hope for a place in yourbook.”