A more disreputable-looking front door I have not seen,—­it was in perfect harmony with the remainder of the establishment.  The paint was off; the woodwork was scratched and dented; the knocker was red with rust.  When Sydney took it in his hand I was conscious of quite a little thrill.  As he brought it down with a sharp rat-tat, I half expected to see the door fly open, and disclose some gruesome object glaring out at us.  Nothing of the kind took place; the door did not budge,—­nothing happened.  Sydney waited a second or two, then knocked again; another second or two, then another knock.  There was still no sign of any notice being taken of our presence.  Sydney turned to Mr Holt.

‘Seems as if the place was empty.’

Mr Holt was in the most singular condition of agitation,—­it made me uncomfortable to look at him.

’You do not know,—­you cannot tell; there may be someone there who hears and pays no heed.’

‘I’ll give them another chance.’

Sydney brought down the knocker with thundering reverberations.  The din must have been audible half a mile away.  But from within the house there was still no sign that any heard.  Sydney came down the step.

‘I’ll try another way,—­I may have better fortune at the back.’

He led the way round to the rear, Mr Holt and I following in single file.  There the place seemed in worse case even than in the front.  There were two empty rooms on the ground floor at the back,—­there was no mistake about their being empty, without the slightest difficulty we could see right into them.  One was apparently intended for a kitchen and wash-house combined, the other for a sitting-room.  There was not a stick of furniture in either, nor the slightest sign of human habitation.  Sydney commented on the fact.

’Not only is it plain that no one lives in these charming apartments, but it looks to me uncommonly as if no one ever had lived in them.’

To my thinking Mr Holt’s agitation was increasing every moment.  For some reason of his own, Sydney took no notice of it whatever, —­possibly because he judged that to do so would only tend to make it worse.  An odd change had even taken place in Mr Holt’s voice,—­ he spoke in a sort of tremulous falsetto.

‘It was only the front room which I saw.’

’Very good; then, before very long, you shall see that front room again.’

Sydney rapped with his knuckles on the glass panels of the back door.  He tried the handle; when it refused to yield he gave it a vigorous shaking.  He saluted the dirty windows,—­so far as succeeding in attracting attention was concerned, entirely in vain.  Then he turned again to Mr Holt,—­half mockingly.

’I call you to witness that I have used every lawful means to gain the favourable notice of your mysterious friend.  I must therefore beg to stand excused if I try something slightly unlawful for a change.  It is true that you found the window already open; but, in my case, it soon will be.’