He barely touched my extended hand, but instantly turned and walked to the bay window.  Descending to the street, I had immediate confirmation of Coverly’s statement that his movements were watched.

In the porch below a man stood talking to the hall-porter.  As I appeared he immediately averted his face and began to light a cigarette.  Nevertheless I had had time to recognize him as the man who had brought Gatton news of Marie’s detention.

It was in a truly perturbed frame of mind that I proceeded on my way to the Planet offices.  I would have sacrificed much to have been afforded means to comfort Isobel; a furious anger towards the man who thus deliberately had brought doubt and unhappiness upon her had taken up permanent quarters in my mind.  I counted Coverly’s declination to clear himself little better than the attitude of a cad.

I read religiously through a pile of cuttings bearing upon the case, and found the unmistakable trend of opinion to be directed towards Coverly as the culprit.  The use made of Isobel’s name enraged me to boiling point and I presently took up the entire bundle of cuttings and crammed them into a waste-paper basket.  I was engaged in stamping them down with my foot when I was called to the telephone.

Inspector Gatton was speaking from New Scotland Yard; and his voice was very grave.

“Can you possibly come along at once?” he asked.  “There is a new development; a most unpleasant one.”

He would say no more over the telephone.  Therefore I hurried out to where Coates was waiting, and in ten minutes found myself in one of those bare, comfortless apartments which characterize the headquarters of the Metropolitan Police Force.

With his hat off Gatton looked more like a seaman than ever, for he had short, crisply curly hair and that kind of bull-dog line of cranium which one associates with members of the senior service.  Upon a chair set in a recess formed by one of the lofty windows a leather grip rested.  It was wet and stained, and had palpably been recovered but recently from the water.  Seeing my glance straying towards this object at the moment of my entrance, the Inspector nodded.

“Yes,” said he, “it has just come in.”

“What is it?”

“Well,” replied Gatton, sitting upon a corner of the table and folding his arms, “it is a piece of evidence sufficient to hang the most innocent man breathing.”

He eyed me in a significant manner and I felt my heart beginning to beat more rapidly.

“May I know the particulars?”

“Certainly.  I asked you to come along for the purpose of telling you.  Sir Eric Coverly’s refusal to answer the questions put to him had necessitated his being watched, as you know.  I mean to say, it’s sheerly automatic; the Commissioner himself couldn’t make an exception.  Well, last night he left his chambers and started for Miss Merlin’s flat.  He came out of a back door and went along a narrow passage, instead of going out at the front.  He evidently thought he had got away unobserved.  He was carrying—­that.”