“I could and would trust my chauffeur with my last shilling,” answered Allerdyke.  “And as for his brother, I’ll take my man’s word for him.  Besides, they both know—­or Mr. Gaffney knows—­that I’m a pretty generous paymaster.  If a man does aught for me, and does it well, he profits to a nice penny!”

“A good argument,” agreed Chettle.  “I don’t know that you could beat it, Mr. Allerdyke.  Well, well—­we’re getting to something and to somewhere!  Now, as you’ve told me all this, I’ll just keep things quiet until I’ve met you and your manager to-morrow, with these two Gaffneys—­we’ll have a conference.  I won’t go near the Yard until after that.  Eleven o’clock to-morrow, then, at your warehouse in Gresham Street.”

He presently replaced the watch and the postcard in an inner pocket, and took his leave, and Allerdyke, letting him out, walked along the corridor with him as far as the lift.  And as Allerdyke turned back to his own room, the third event of that day happened, and seemed to him to be the most surprising and important one of all.

What made Allerdyke pause as he retraced his steps along the corridor, pause to look over the balustrade to the floor immediately below his own, he never knew nor could explain.  But, just as he was about to re-enter his room, he did so pause, leaning over the railings and looking down for a moment.  In that moment he saw Mrs. Marlow.

A considerable portion of the floor immediately beneath him was fully exposed to the view of any one leaning over the balustrade as Allerdyke did.  This was a quiet part of the hotel, a sort of wing cut away from the main building; the floor at which he was looking was given up to private suites of rooms, one of them, a larger one than the others, being Fullaway’s, which filled one side of the corridor; the others were suites of two, in some cases of three rooms.  As he looked over and down, Allerdyke suddenly saw a door open in one of these smaller suites—­open silently and stealthily.  Then he saw Mrs. Marlow look out, and she glanced right and left about her.  The next instant, she emerged from the room with the same stealthiness, closed and locked the door with a key which she immediately pocketed, slipped along the corridor, and disappeared into Franklin Fullaway’s suite.  It was all over in less than a minute, and Allerdyke turned into his own door, smiling cynically to himself.

“She looked right and left, but she forgot to look up!” he muttered.  “Ah! those small details.  And what does that mean?  Anyway, I know which door she came out of!”

He glanced at his watch—­precisely half-past eleven.  He made a note of the time in his pocket-book and went to bed.  And next morning, rising early, as was his custom, he descended to the ground floor by means of the stairs instead of the lift, and as he passed the door from which he had seen Mrs. Marlow emerge he mentally registered the number.  Fifty-three.  Number fifty-three.