海奇驚訝地盯著他。幾分鍾後，教授站起來走進隔壁的房間，這時電話鈴響了。教授回來後，拿起帽子，然後和海奇一起走了出去。
他們把證件遞出去的時候，德·勒賽普斯正好在家，並且接待了他們。在他們談論該案子的十幾分鍾內，“思想機器”不斷地來回打量著房間內的一切。這時，外麵響起了敲門聲。
“馬洛裏警官來了，海奇先生，”“思想機器”說，“請幫他開門。”
德·勒賽普斯的眼中顯出一絲恐慌，但是隨即隱去。馬洛裏進來的時候一臉的疑惑。
“馬洛裏警官，”“思想機器”平靜地說，“我們該好好地欣賞一下壁爐上麵這幅惠斯勒的畫。多美啊！你還記得看過的原作嗎？”
馬洛裏嘟囔了一聲。德·勒賽普斯的臉上沒有流露出絲毫因為得到讚美而表現出來的得意之情，相反，他的臉瞬間變得蒼白，雙手緊握成拳。但是，他很快恢複了平靜，麵帶微笑。
“它的美妙之處不僅僅在於它忠實於原作，”科學家說道，“還在於畫家在創作它時所處的特殊的環境。比如，我不知道馬洛裏警官是否了解，如果把膠水、油灰和其他一些常見的材料和成黏稠物質的話，那就可以很輕鬆地用它來掩蓋油畫並作為畫布，同時又不會損傷原來的畫。”
“這張水彩畫，也就是惠斯勒的這幅畫，”“思想機器”繼續說道，“就是畫在我剛才提到的那種物質上的。它的下麵就是魯本斯的畫，它可以在不損傷下麵油畫的前提下被除去。所以，我們看到的並不是惠斯勒的水彩畫，而是價值五萬美元的魯本斯的名作。對不對，德·勒賽普斯先生？”
德·勒賽普斯沒有回答，也沒必要回答。一個小時後，他就被關進了警察局的牢房。而海奇則在電話中問了“思想機器”一個他百思不解的問題：
“你怎麽知道水彩畫是畫在魯本斯的油畫上的？”
“因為這是唯一可以讓人找不到魯本斯的原畫，同時還能避免它受到損傷的方法。”“思想機器”答道，“我告訴過你，德·勒賽普斯是個聰明人，動動腦筋就能想到。海奇先生，二加二不是有時才等於四，而是永遠等於四。”
Matthew Kale made fifty million dollars out of axle grease， after which he began to patronize the high arts. It was simple enough：he had the money， and Europe had the old masters.His method of buying was simplicity itself.There were five thousand square yards， more or less， in the huge gallery of his marble mansion which were to be covered， so he bought five thousand square yards， more or less， of art.Some of it was good， some of it fair， and much of it bad.The chief picture of the collection was a Rubens， which he had picked up in Rome for fifty thousand dollars.
Soon after acquiring his collection， Kale decided to make certain alterations in the vast room where the pictures hung. They were all taken down and stored in the ball room， equally vast， with their faces toward the wall.Meanwhile Kale and his family took refuge in a nearby hotel.
It was at this hotel that Kale met Jules de Lesseps. De Lesseps was distinctly French， the sort of Frenchman whose conversation resembles calisthenics.He was nervous， quick， and agile， and he told Kale in confidence that he was not only a painter himself， but was a connoisseur in the high arts.Pompous in the pride of possession， Kale went to a good deal of trouble to exhibit his private collection for de Lesseps'delectation.It happened in the ball room， and the true artist's delight shone in the Frenchman's eyes as he handled the pieces which were good.Some of the others made him smile， but it was an inoffensive sort of smile.
With his own hands Kale lifted the precious Rubens and held it before the Frenchman's eyes. It was a"Madonna and Child，"one of those wonderful creations which have endured through the years with all the sparkle and color beauty of their pristine days.Kale seemed disappointed because de Lesseps was not particularly enthusiastic about this picture.
"Why， it's a Rubens！"he exclaimed.
"Yes， I see，"replied de Lesseps.
"It cost me fifty thousand dollars."
"It is perhaps worth more than that，"and the Frenchman shrugged his shoulders as he turned away.
Kale looked at him in chagrin. Could it be that de Lesseps did not understand that it was a Rubens， and that Rubens was a painter？Or was it that he had failed to hear him say that it cost him fifty thousand dollars？Kale was accustomed to seeing people bob their heads and open their eyes when he said fifty thousand dollars；therefore，
"Don't you like it？"he asked.
"Very much indeed，"replied de Lesseps，"but I have seen it before. I saw it in Rome just a week or so before you purchased it."
They rummaged through the pictures， and at last a Whistler was turned up for their inspection. It was one of the famous Thames series， a water color.De Lesseps'face radiated excitement， and several times he glanced from the water color to the Rubens as if mentally comparing the exquisitely penciled and colored modern work with the bold， masterly technic of the old.
Kale misunderstood the silence."I don't think much of this one myself，"he explained apologetically."It's a Whistler， and all that， and it cost me five thousand dollars， and I sort of had to have it， but still it isn't just the kind of thing that I like. What do you think of it？"
"I think it is perfectly wonderful！"replied the Frenchman enthusiastically."It is the essence， the superlative， of modern work. I wonder if it would be possible，"and he turned to face Kale，"for me to make a copy of that？I have some slight skill in painting myself， and dare say I could make a fairly creditable copy of it."
Kale was flattered. He was more and more impressed each moment with the picture."Why， certainly，"he replied."I will have it sent up to the hotel， and you can-"
"No， no， no！"interrupted de Lesseps quickly."I wouldn't care to accept the responsibility of having the picture in my charge. There is always a danger of fire.But if you would give me permission to come here-this room is large and airy and light， and besides it is quiet-"
"Just as you like，"said Kale magnanimously."I merely thought the other way would be most convenient for you."
De Lesseps drew near， and laid one hand on the millionaire's arm."My dear friend，"he said earnestly，"if these pictures were my pictures， I shouldn't try to accommodate anybody where they were concerned. I dare say the collection as it stands cost you-"
"Six hundred and eighty-seven thousand dollars，"volunteered Kale proudly.
"And surely they must be well protected here in your house during your absence？"
"There are about twenty servants in the house while the workmen are making the alterations，"said Kale，"and three of them don't do anything but watch this room. No one can go in or out except by the door we entered-the others are locked and barred-and then only with my permission， or a written order from me.No， sir， nobody can get away with anything in this room."
"Excellent， excellent！"said de Lesseps admiringly. He smiled a little bit."I am afraid I did not give you credit for being the far-sighted business man that you are."He turned and glanced over the collection of pictures abstractedly."A clever thief， though，"he ventured，"might cut a valuable painting， for instance the Rubens， out of the frame， roll it up， conceal it under his coat， and escape."
Kale laughed pleasantly and shook his head.
It was a couple of days later at the hotel that de Lesseps brought up the subject of copying the Whistler. He was profuse in his thanks when Kale volunteered to accompany him to the mansion and witness the preliminary stages of the work.They paused at the ball room door.
"Jennings，"said Kale to the liveried servant there，"this is Mr de Lesseps. He is to come and go as he likes.He is going to do some work in the ball room here.See that he isn't disturbed."
De Lesseps noticed the Rubens leaning carelessly against some other pictures， with the holy face of the Madonna toward them."Really， Mr Kale，"he protested，"that picture is too valuable to be left about like that. If you will let your servants bring me some canvas， I shall wrap it and place it up on the table here off the floor.Suppose there were mice here！"
Kale thanked him. The necessary orders were given， and finally the picture was carefully wrapped and placed beyond harm's reach， whereupon de Lesseps adjusted himself， paper， easel， stool， and all， and began his work of copying.There Kale left him.
Three days later Kale just happened to drop in， and found the artist still at his labor.
"I just dropped by，"he explained，"to see how the work in the gallery was getting along. It will be finished in another week.I hope I am not disturbing you？"
"Not at all，"said de Lesseps，"I have nearly finished. See how I am getting along？"He turned the easel toward Kale.
The millionaire gazed from that toward the original which stood on a chair near by， and frank admiration for the artist's efforts was in his eyes."Why， it's fine！"he exclaimed."It's just as good as the other one， and I bet you don't want any five thousand dollars for it-eh？"
That was all that was said about it at the time. Kale wandered about the house for an hour or so， then dropped into the ball room where the artist was just getting his paraphernalia together， and they walked back to the hotel.The artist carried under one arm his copy of the Whistler， loosely rolled up.
One week passed， and the workmen who had been engaged in refinishing and decorating the gallery had gone. De Lesseps volunteered to assist in the work of rehanging the pictures， and Kale gladly turned the matter over to him.It was in the afternoon of the day this work began that de Lesseps， chatting pleasantly with Kale， ripped loose the canvas which enshrouded the precious Rubens.Then he paused with an exclamation of dismay.The picture was gone；the frame which had held it was empty.A thin strip of canvas around the inside edge showed that a sharp penknife had been used to cut out the painting.
All of these facts came to the attention of Professor Augustus S. F.X.Van Dusen-The Thinking Machine.This was a day or so after Kale had rushed into Detective Mallory's office at police headquarters， with the statement that his Rubens had been stolen.He banged his fist down on the detective's desk and roared at him."It cost me fifty thousand dollars！"he declared violently."Why don't you do something？What are you sitting there staring at me for？"
"Don't excite yourself， Mr Kale，"the detective advised."I will put my men at work right now to recover the-the-What is a Rubens， anyway？"
"It's a picture！"bellowed Mr Kale."A piece of canvas with some paint on it， and it cost me fifty thousand dollars-don't you forget that！"
So the police machinery was set in motion to recover the painting. And in time the matter fell under the watchful eye of Hutchinson Hatch， reporter.He learned the facts preceding the disappearance of the picture， and then called on de Lesseps.He found the artist in a state of excitement bordering on hysteria；an intimation from the reporter of the object of his visit caused de Lesseps to burst into words.
"Mon Dieu！It is outrageous！"he exclaimed."What can I do？I was the only one in the room for several days. I was the one who took such pains to protect the picture.And now it is gone！The loss is irreparable.What can I do？"