The officer nodded:

"I ought to know that foot-print," he said. "It's all over the roads in northern France."

"We made inquiries through you," the detective resumed, "and when I found that this Gunner Barling, the owner of the pa.s.s, was missing, well, you will admit, it looked a bit suspicious."

"Still, you know," the A.P.M. objected, "this man appears to have the most excellent character. He's got a clean sheet; he's never gone absent before. And he's been out with his battery almost since the beginning of the war."

"I'm not making any charge against him as yet," answered the detective, picking up his hat, "but it would interest me very much, very much indeed, Captain Beardiston, to have five minutes'

chat with this gunner. And so I ask you to keep a sharp lookout for a man answering to his description, and if you come across him, freeze on to him hard, and give me a ring on the telephone."

"Right you are," said the officer, "I'll hold him for you, Mr.

Marigold. But I hope your suspicions are not well-founded."

For a brief moment the detective became a human being.

"And so do I, if you want to know," he said. "One can forgive those lads who are fighting out there almost anything. I've got a boy in France myself!"

A little sigh escaped him, and then Mr. Marigold remembered "The Yard."

"I'll bid you good-day!" he added in his most official voice and took his leave.

He walked down the steps by the Duke of York's column and through the Horse Guards into Whitehall, seemingly busy with his own thoughts. A sprucely dressed gentleman who was engaged in the exciting and lucrative sport of war profiteering turned color and hastily swerved out towards the Park as he saw the detective crossing the Horse Guards' Parade. He was unpleasantly reminded of making the acquaintance of Mr. Marigold over a bucketshop a few years ago with the result that he had vanished from the eye of his friends for eighteen months. He congratulated himself on thinking that Mr. Marigold had not seen him, but he would have recognized his mistake could he but have caught sight of the detective's face. A little smile flitted across Mr. Marigold's lips and he murmured to himself:

"Our old friend is looking very prosperous just now. I wonder what he's up to?"

Mr. Marigold didn't miss much.

The detective made his way to the Chief's office. Barbara Mackwayte, in a simple black frock with white linen collar and cuffs, was at her old place in the ante-room. A week had elapsed since the murder, and the day before, Mr. Marigold knew, the mortal remains of poor old Mackwayte had been laid to rest. He was rather surprised to see the girl back at work so soon.

She did not speak to him as she showed him into the Chief, but there was a question lurking in her gray eyes.

Mr. Marigold looked at her and gravely shook his head.

"Nothing fresh," he said.

The Chief was unusually exuberant. Mr. Marigold found him surrounded, as was his wont, by papers, and a fearsome collection of telephone receivers. He listened in silence to Mr. Marigold's account of his failure to trace Barling.

"Marigold," he said, when the other had finished, "we must undoubtedly lay hold of this fellow. Let's see now... ah! I have it!"

He scribbled a few lines on a writing-pad and tossed it across to the detective.

"If your friend's innocent," he chuckled, "that'll fetch him to a dead certainty. If he murdered Mackwayte, of course he won't respond. Read it out and let's hear how it sounds!"

The Chief leaned back in his chair and lit a cigarette while the detective read out:

"If Gunner Barling, etcetera, etcetera, will communicate with Messrs. Blank and Blank, solicitors, he will hear of something to his advantage. Difficulties with the military can be arranged."

"But I say, sir," objected Mr. Marigold, "the military authorities will hardly stand for that last, will they?"

"Won't they, by Jove" retorted the Chief grimly. "They will if I tell 'em to. No official soullessness for me; thank you! And now, Marigold, just ask Matthews to fill in Barling's regimental number and all that and the name and address of the solicitors who do this kind of thing for us. And tell him we'll insert the ad. daily until further notice in the Mail, Chronicle, Daily News, Sketch, Mirror, Evening News..."

"And Star," put in Mr. Marigold who had Radical tendencies.

"The Star, too, by all means. That ought to cover the extent of your pal's newspaper reading, I fancy, eh, Marigold! Right!"

He held out a hand in farewell. But Mr. Marigold stood his ground. He was rather a slow mover, and there were a lot of things he wanted to discuss with the Chief.

"I was very sorry to see poor Major Okewood in the casualty list this morning, sir," he said. "I was going to ask you..."

"Ah, terrible, terrible!" said the Chief. Then he added:

"Just tell Miss Mackwayte I want her as you go out, will you?"

The detective was used to surprises but the Chief still bowled him out occasionally. Before he knew what he was doing, Mr.

Marigold found himself in the ante-room doing as he was bid.

As soon as her father's funeral was over; Barbara had insisted on returning to work. The whole ghastly business of the murder and the inquest that followed seemed to her like a bad dream which haunted her day and night. By tacit consent no one in the office had made any further allusion, to the tragedy. She had just slipped back into her little niche, prompt, punctual, efficient as ever.

"No, it's not for the letters," the Chief said to her as she came in with her notebook and pencil. "I'm going to give you a little trip down to the country this afternoon, Miss Mackwayte... to, Ess.e.x... the Mill House, Wentfield... you know whom it is you are to see, eh? I'm getting a little restless as we've had no reports since he arrived there. I had hoped, by this, to have been able to put him on the track of Nur-el-Din, but, for the moment, it looks as if we had lost the scent. But you can tell our friend all we know about the lady's antecedents--what we had from my French colleague the other day, you know? Let him have all the particulars about this Barling case--you know about that, don't you? Good, and, see here, try and find out from our mutual friend what he intends doing. I don't want to rush him... don't let him think that... but I should rather like to discover whether he has formed any plan. And now you get along. There's a good train about three which gets you down to Wentfield in just under the hour. Take care of yourself! See you in the morning!"

Pressing a bell with one hand and lifting up a telephone receiver with the other, the Chief immersed himself again in his work. He appeared to have forgotten Miss Mackwayte's very existence.

At a quarter to five that evening, Barbara unlatched the front gate of the Mill House and walked up the drive. She had come on foot from the station and the exercise had done her good. It had been a deliciously soft balmy afternoon, but with the fall of dusk a heavy mist had come creeping up from the sodden, low-lying fields and was spreading out over the neglected garden of Mr.

Bellward's villa as Barbara entered the avenue.

The damp gloom of the place, however, depressed her not at all.

She exulted in the change of scene and the fresh air; besides, she knew that the presence of Desmond Okewood would dispel the vague fears that had hung over her incessantly ever since her father's murder. She had only met him twice, she told herself when this thought occurred to her, but there was something bracing and dependable about him that was just the tonic she wanted.

A porter at the station, who was very intelligent as country porters go, had told her the way to the Mill House. The way was not easy to find for there were various turns to make but, with the aid of such landmarks as an occasional inn, a pond or a barn, given her by the friendly porter, Barbara reached her destination. Under the porch she pulled the handle of the bell, all dank and glistening with moisture, and heard it tinkle loudly somewhere within the house.

How lonely the place was, thought Barbara with a little shiver!

The fog was growing thicker every minute and now seemed suspended like a vast curtain between her and the drive. Somewhere in the distance she heard the hollow gurgling of a stream. Otherwise, there was no sound.

She rang the bell again rather nervously and waited. In her bag she had a little torch-light (for she was a practical young person), and taking it out, she flashed it on the door. It presented a stolid, impenetrable oaken front. She stepped out into the fog and scanned the windows which were already almost lost to view. They were dark and forbidding.

Again she tugged at the bell. Again, with a groaning of wires, responded the hollow tinkle. Then silence fell once more. Barbara began to get alarmed. What had happened to Major Okewood? She had understood that there was no question of his leaving the house until the Chief gave him the word. Where, then, was he? He was not the man to disobey an order. Rather than believe that, she would think that something untoward had befallen him. Had there been foul play here, too?

A sudden panic seized her. She grasped the bell and tugged and tugged until she could tug no more. The bell jangled and pealed and clattered reverberatingly from the gloomy house, and then, with a jarring of wires, relapsed into silence. Barbara beat on the door with her hands, for there was no knocker; but all remained still within. Only the dank mist swirled in ever denser about her as she stood beneath the dripping porch.

"This won't do!" said Barbara, pulling herself together. "I mustn't get frightened, whatever I do! Major Okewood is very well capable of defending himself. What's happened is that the man has been called away and the servants have taken advantage of his absence to go out! Barbara, my dear, you'll just have to foot it back to the station without your tea!"

She turned her back on the door and torch in hand, plunged resolutely into the fog-bank. The mist was bewilderingly thick.

Still, by going slow and always keeping the gravel under her feet, she reached the front gate and turned out on the road.

Here the mist was worse than ever. She had not taken four paces before she had lost all sense of her direction. The gate, the railways, were gone. She was groping in a clinging pall of fog.

Her torch was worse than useless. It only illuminated swirling swathes of mist and confused her, so she switched it out. In vain she looked about her, trying to pick up some landmark to guide her. There was no light, no tree, no house visible, nothing but the dank, ghostly mist.