n the back of the envelope was the name of a
West End dressmaker.

"'That is of no use to me,' Lyle said. He took out his card and showed
it to the postman. 'I am Inspector Lyle from Scotland Yard,' he said.
'The people in this house are under arrest. Everything it contains is
now in my keeping. Did you deliver any other letters here this morning!'

"The man looked frightened, but answered promptly that he was now upon
his third round. He had made one postal delivery at seven that morning
and another at eleven.

"'How many letters did you leave here!' Lyle asked.

"'About six altogether,' the man answered.

"'Did you put them through the door into the letter-box!'

"The postman said, 'Yes, I always slip them into the box, and ring and
go away. The servants collect them from the inside.'

"'Have you noticed if any of the letters you leave here bear a Russian
postage stamp!' Lyle asked.

"The man answered, 'Oh, yes, sir, a great many.'

"'From the same person, would you say!'

"'The writing seems to be the same,' the man answered. 'They come
regularly about once a week--one of those I delivered this morning had a
Russian postmark.'

"'That will do,' said Lyle eagerly. 'Thank you, thank you very much.'

"He ran back into the hall, and, pulling out his penknife, began to pick
at the lock of the letter-box.

"'I have been supremely careless,' he said in great excitement. 'Twice
before when people I wanted had flown from a house I have been able to
follow them by putting a guard over their mail-box. These letters, which
arrive regularly every week from Russia in the same handwriting, they
can come but from one person. At least, we shall now know the name of
the master of this house. Undoubtedly it is one of his letters that the
man placed here this morning. We may make a most important discovery.'

"As he was talking he was picking at the lock with his knife, but he
was so impatient to reach the letters that he pressed too heavily on the
blade and it broke in his hand. I took a step backward and drove my
heel into the lock, and burst it open. The lid flew back, and we pressed
forward, and each ran his hand down into the letterbox. For a moment we
were both too startled to move. The box was empty.

"I do not know how long we stood staring stupidly at each other, but
it was Lyle who was the first to recover. He seized me by the arm and
pointed excitedly into the empty box.

"'Do you appreciate what that means