“I figured, since the murder had been made to look so much like a natural death, that he’d come out here some time to-day, expecting to carry it off.  I wanted to go to the station, anyway, to find out if he’d been seen coming through last night or early this morning.  While I was talking to the station agent I had my one piece of luck.  I couldn’t believe my eyes.  Mr. Robert walks up from the woods.  He’d been hiding around the neighbourhood all the time.  Probably had missed his handkerchief and decided he’d better not take any chances.  Yet it must have seemed a pretty sure thing that the station wouldn’t be watched, and it’s those nervy things, doing the obvious, that skilful criminals get away with all the time.  I needed only one look at him, and I had the answer to the mystery of the footprints.  I gave him plenty of time to come here and change his clothes, then I manoeuvered him out of his room and went there and found the pumps he’d worn last night and to-day.  You see, they’d be a little smaller than his ordinary shoes.  Not only did they fit the footprints exactly, but they were stained with soil exactly like that in the court.  There you are, sir.  I’ve made a plaster cast of one of the prints.  I’ve got it here in my pocket where I intend to keep it until I clear the whole case up and turn in my report.”

Graham’s tone was shocked and discouraged.

“What more do you want?  Why haven’t you arrested him?”

In this room the detective’s satisfied chuckle was an offence.

“No good detective would ask that, Mr. Graham.  I want my report clean.  The coroner will tell us how the old man was killed.  I want to tell how young Blackburn got into that room.  One of the windows was raised a trifle, but that’s no use.  I’ve figured on the outside of the wing until I’m dizzy.  There’s no way up for a normal man.  An orangoutang would make hard work of it.  His latch key would have let him into the house, and it would have been simple enough for him to find out that the old man had changed his room.  I’ve got to find out how he got past those doors, locked on the inside.”

He chuckled again.

“Almost like a sleep-walker’s work.”

Bobby shivered.  Was that where the evidence pointed?  Already the net was too finely woven.  The detective continued earnestly: 

“I’m figuring on some scheme to make him show me the way.  I’ve a sort of plan for to-night, but it’s only a chance.”

“What?” Graham asked.

“Oh, no, sir,” Howells laughed.  “You’ll learn about that when the time comes.”

“I don’t understand you,” Graham said.  “You’re sure of your man but you keep no close watch on him.  Do you know where he is now?”

“Haven’t the slightest idea, Mr. Graham.”

“What’s to prevent his running away?”

“I’m offering him every opportunity.  He wouldn’t get far, and I’ve a feeling that if he confessed by running he’d break down and give up the whole thing.  You’ve no idea how it frets me, Mr. Graham.  I’ve got my man practically in the chair, but from a professional point of view it isn’t a pretty piece of work until I find out how he got in and out of that room.  The thing seems impossible, and yet here we are, knowing that he did it.  Well, maybe I’ll find out to-night.  Hello!”