"But how could you guess what the motive was?"
"可是，你是怎么猜出他的动机的呢？"
"Had there been women in the house, I should have suspected a mere vulgar intrigue.
"如果在那店铺里有女人的话，我本来会怀疑无非是搞些庸俗的风流事。
That, however, was out of the question.
可是，根本不是那么回事。
The man's business was a small one,
这个当铺老板做的是小本经营的买卖，
and there was nothing in his house which could account for such elaborate preparations, and such an expenditure as they were at.
当铺里没有什么值钱的东西，值不得他们如此精心策划，花那么多钱。
It must, then, be something out of the house. What could it be?
因此，他们的目标肯定不在当铺。那么可能搞什么呢？

I thought of the assistant's fondness for photography, and his trick of vanishing into the cellar.
我想到这个伙计喜欢照相，想到他经常出没于地下室这个诡计。
The cellar! There was the end of this tangled clue.
地下室！这就找到了这个错综复杂的案件的线索。
Then I made inquiries as to this mysterious assistant
然后，我调查了这个神秘的伙计的情况。
and found that I had to deal with one of the coolest and most daring criminals in London.
我发现，我的对手是伦敦头脑最冷静、胆子最大的罪犯之一，
He was doing something in the cellar–something which took many hours a day for months on end.
他在地下室里搞了名堂，而且要连续几个月每天干许多小时才行。
What could it be, once more? I could think of nothing save that he was running a tunnel to some other building.
那再问一下，可能搞什么呢？我想除了挖一条通往其他楼房的地道以外，不可能是其他什么东西。
So far I had got when we went to visit the scene of action.
当我们去察看作案地点时，我心里就明白了。