The third flight of stairs ended in a straight passage of somelength， with a great picture in Indian tapestry upon the right ofit and three doors upon the left. Holmes advanced along it in thesame slow and methodical way， while we kept close at his heels，with our long black shadows streaming backwards down thecorridor. The third door was that which we were seeking. Holmesknocked without receiving any answer， and then tried to turn thehandle and force it open. It was locked on the inside， however，and by a broad and powerful bolt， as we could see when we set ourlamp up against it. The key being turned， however， the hole wasnot entirely closed. Sherlock Holmes bent down to it and instantlyrose again with a sharp intaking of the breath.
“There is something devilish in this， Watson，” said he， moremoved than I had ever before seen him. “What do you make of it？”
I stooped to the hole and recoiled in horror. Moonlight wasstreaming into the room， and it was bright with a vague and shiftyradiance. Looking straight at me and suspended， as it were， inthe air， for all beneath was in shadow， there hung a face—thevery face of our companion Thaddeus. There was the same high，shining head， the same circular bristle of red hair， the samebloodless countenance. The features were set， however， in ahorrible smile， a fixed and unnatural grin， which in that still andmoonlit room was more jarring to the nerves than any scowl orcontortion. So like was the face to that of our little friend thatI looked round at him to make sure that he was indeed with us.
Then I recalled to mind that he had mentioned to us that hisbrother and he were twins.
“This is terrible！” I said to Holmes. “What is to be done？”
“The door must come down，” he answered， and springingagainst it， he put all his weight upon the lock.
It creaked and groaned but did not yield. Together we flungourselves upon it once more， and this time it gave way with asudden snap， and we found ourselves within Bartholomew Sholto’schamber.
It appeared to have been fitted up as a chemical laboratory. Adouble line of glass-stoppered bottles was drawn up upon the wallopposite the door， and the table was littered over with Bunsenburners， test-tubes， and retorts. In the corners stood carboys ofacid in wicker baskets. One of these appeared to leak or to havebeen broken， for a stream of dark-colored liquid had trickled outfrom it， and the air was heavy with a peculiarly pungent， tarlikeodor. A set of steps stood at one side of the room in the midst of alitter of lath and plaster， and above them there was an opening inthe ceiling large enough for a man to pass through. At the foot ofthe steps a long coil of rope was thrown carelessly together.
By the table in a wooden armchair the master of the house wasseated all in a heap， with his head sunk upon his left shoulderand that ghastly， inscrutable smile upon his face. He was stiff andcold and had clearly been dead many hours. It seemed to me thatnot only his features but all his limbs were twisted and turned inthe most fantastic fashion. By his hand upon the table there laya peculiar instrument—a brown， close-grained stick， with a stonehead like a hammer， rudely lashed on with coarse twine. Beside itwas a torn sheet of note-paper with some words scrawled upon it.
Holmes glanced at it and then handed it to me.
“You see，” he said with a significant raising of the eyebrows.
In the light of the lantern I read with a thrill of horror， “Thesign of the four.”
“In God’s name， what does it all mean？” I asked.
“It means murder，” said he， stooping over the dead man. “Ah Iexpected it. Look here！”
He pointed to what looked like a long dark thorn stuck in theskin just above the ear.
“It looks like a thorn，” said I.
“It is a thorn. You may pick it out. But be careful， for it ispoisoned.”
I took it up between my finger and thumb. It came away fromthe skin so readily that hardly any mark was left behind. One tinyspeck of blood showed where the puncture had been.
“This is all an insoluble mystery to me，” said I. “It grows darkerinstead of clearer.”
“On the contrary，” he answered， “it clears every instant. I onlyrequire a few missing links to have an entirely connected case.”
We had almost forgotten our companion’s presence since weentered the chamber. He was still standing in the doorway， thevery picture of terror， wringing his hands and moaning to himself.
Suddenly， however， he broke out into a sharp， querulous cry.
“The treasure is gone！” he said. “They have robbed him of thetreasure！ There is the hole through which we lowered it. I helpedhim to do it！ I was the last person who saw him！ I left him herelast night， and I heard him lock the door as I came downstairs.”
“What time was that？”
“It was ten o’clock. And now he is dead， and the police will becalled in， and I shall be suspected of having had a hand in it. Oh，yes， I am sure I shall. But you don’t think so， gentlemen？ Surelyyou don’t think that it was I？ Is it likely that I would have broughtyou here if it were I？ Oh， dear！ oh， dear！ I know that I shall gomad！”
He jerked his arms and stamped his feet in a kind of convulsivefrenzy.
“You have no reason for fear， Mr. Sholto，” said Holmes kindly，putting his hand upon his shoulder； “Take my advice and drivedown to the station to report the matter to the police. Offer toassist them in every way. We shall wait here until your return.”
The little man obeyed in a half-stupefied fashion， and we heardhim stumbling down the stairs in the dark.
Sherlock Holmes Gives a Demonstration
“Now， Watson，” said Holmes， rubbing his hands， “we have halfan hour to ourselves. Let us make good use of it. My case is， as Ihave told you， almost complete； but we must not err on the sideof overconfidence. Simple as the case seems now， there may besomething deeper underlying it.”