“The key!” he cried.  “Come on, quick!”

He thrust it into the lock and turned it; the door swung smoothly open.  The policeman laid his hand upon Tavernake’s shoulder.

“Look here,” he said, “let’s have that story of yours again, a little more clearly.  Who is it that’s in this house?”

“Five minutes ago,” Tavernake began, speaking rapidly, “I met a man in the Strand whom I know slightly—­Pritchard, an American detective.  He said that he had something to say to me and he asked me to walk round with him to a club in this Terrace.  We were in the middle of the road there, talking, when a man sprang at him; he must have come up behind quite noiselessly.  The man had a knife in his hand.  My friend threw him head over heels —­ it was some trick of jiu-jutsu; I have seen it done at the Polytechnic.  He fell in front of this door which must either have been ajar or else some one who was waiting must have let him in.  He crawled through and my friend followed him.  The door was slammed in my face.”

“How long ago was this?” the policeman asked.

“Not much more than five minutes,” Tavernake answered.

The policeman coughed.

“It’s a very queer story, sir.”

“It’s true!” Tavernake declared, fiercely.  “You and I have got to search this house.”

The policeman nodded.

“There’s no harm in that, sir, anyway.”

He flashed his lantern around the hall—­unfurnished, with paper hanging from the walls.  Then they began to enter the rooms, one by one.  Nowhere was there any sign of occupation.  From floor to floor they passed, in grim silence.  In the front chamber of the attic was a camp bedstead, two or three humble articles of furniture, and a small stove.

“Caretaker’s kit,” the policeman muttered.  “Nothing seems to have been used for some time.”

They descended the stairs again.

“You say you saw the two men enter this house, sir?” the policeman remarked doubtfully.

“I did,” Tavernake declared.  “There is no doubt about it.”

“The back entrances are all properly locked,” the policeman pointed out.  “None of the windows by which any one could escape have been opened.  We’ve been into every room.  There’s no one in the house now, sir, is there?”

“There doesn’t seem to be,” Tavernake admitted.

The policeman looked him over once more; Tavernake certainly had not the appearance of one attempting a hoax.

“I am afraid there is nothing more we can do, sir,”

the man said civilly.  “You had better give me your name and address.”

“Can’t we go over the place once more?” Tavernake suggested.  “I tell you I saw them come in.”

“I have my beat outside to look after, sir,” the constable answered.  “If it wasn’t that you seem respectable, I should begin to think that you wanted me out of the way for a bit.  Name and address, please.”