“Yes, she is, by a most disastrous coincidence.  But what are we to do?  Good God!  Dr. Thorndyke, they have taken her to prison—­to prison—­think of it!  My poor Edith!”

“We’ll soon have her out,” said Thorndyke.  “But listen; there is someone at the door.”

A brisk rat-tat confirmed his statement; and when I rose to open the door, I found myself confronted by Inspector Badger.  There was a moment of extreme awkwardness, and then both the detective and Mr. Curtis proposed to retire in favour of the other.

“Don’t go, inspector,” said Thorndyke; “I want to have a word with you.  Perhaps Mr. Curtis would look in again, say, in an hour.  Will you?  We shall have news for you by then, I hope.”

Mr. Curtis agreed hastily, and dashed out of the room with his characteristic impetuosity.  When he had gone, Thorndyke turned to the detective, and remarked dryly: 

“You seem to have been busy, inspector?”

“Yes,” replied Badger; “I haven’t let the grass grow under my feet; and I’ve got a pretty strong case against Miss Curtis already.  You see, she was the last person seen in the company of the deceased; she had a grievance against him; she is left-handed, and you remember that the murder was committed by a left-handed person.”

“Anything else?”

“Yes.  I have seen those Italians, and the whole thing was a put-up job.  A woman, in a widow’s dress and veil, paid them to go and play the fool outside the building, and she gave them the letter that was left with the porter.  They haven’t identified her yet, but she seems to agree in size with Miss Curtis.”

“And how did she get out of the chambers, with the door bolted on the inside?”

“Ah, there you are!  That’s a mystery at present—­unless you can give us an explanation.”  The inspector made this qualification with a faint grin, and added:  “As there was no one in the place when we broke into it, the murderer must have got out somehow.  You can’t deny that.”

“I do deny it, nevertheless,” said Thorndyke.  “You look surprised,” he continued (which was undoubtedly true), “but yet the whole thing is exceedingly obvious.  The explanation struck me directly I looked at the body.  There was evidently no practicable exit from the flat, and there was certainly no one in it when you entered.  Clearly, then, the murderer had never been in the place at all.”

“I don’t follow you in the least,” said the inspector.

“Well,” said Thorndyke, “as I have finished with the case, and am handing it over to you, I will put the evidence before you seriatim.  Now, I think we are agreed that, at the moment when the blow was struck, the deceased was standing before the fireplace, winding the clock.  The dagger entered obliquely from the left, and, if you recall its position, you will remember that its hilt pointed directly towards an open window.”

“Which was forty feet from the ground.”