"Yes," I said; "I have no doubt the Mediterranean sounds attractive to him. There's a pretty stiff penalty attached to selling Government secrets if you happen to be found out. Besides, I expect he's still worrying a lot about me."

Joyce nodded. "He told me last night that I was the only thing that was keeping him in London. You see I can't quite make up my mind whether I love him well enough to come away."

"That's unfortunate for George," I said. "Latimer will probably act at once as soon as he gets that letter, and directly he does I mean to go straight to Cheyne Walk, unless I'm dead or in prison."

Joyce took my arm. "Neil," she said, "whatever happens you mustn't be arrested. If you think there's any chance of it you must go on board the _Betty_ and take her somewhere down the river. You can let me know at the flat where you are. Promise me you will, Neil. You see if the police once got hold of you, even Latimer mightn't be able to do anything."

For a moment I hesitated. So far I had told Joyce nothing of the wild suspicion about Marks's ident.i.ty which Sonia's revelations had put into my head. I didn't want to rouse hopes in her which might turn out quite baseless. Besides, even if I were really on the right track, and Marks was the man who had betrayed the gang in St. Petersburg, it was quite another thing to prove that they were responsible for splitting his skull. I had nothing to support the idea beyond Joyce's bare word that she had seen McMurtrie in the flat on the afternoon of the murder. Sonia's testimony might have been useful, but after today I could hardly picture her in the witness-box giving evidence on my behalf.

On the whole, therefore, I thought it best for the present to keep the matter to myself. I promised, however, that in the event of my observing anything in the nature of a policeman stealthily approaching the hut I would at once seek sanctuary on the _Betty_--an a.s.surance which might have sounded worthless to some people, but certainly seemed to comfort Joyce.

Anyhow she said good-bye to me with her usual cheerfulness and pluck, and we parted after a last affectionate kiss in full view of the open marsh. Then I returned to the hut suffering from that novel and highly unpleasant sense of loneliness that Joyce's departures had begun to awake in me.

I don't think there is anything much more trying to one's nerves than having to sit and wait for some critical event which may happen at any moment. I have had a good deal of practice at waiting in my life, but I never remember the hours dragging so desperately slowly as they did the remainder of that afternoon.

A dozen times I went over what Latimer and Sonia had told me, putting together their different stories in my mind and trying to think if there was any point I had overlooked. I could see none. The mere way in which they had corroborated each other was enough to make me feel sure that they were both speaking the truth. Besides, everything that had happened from the moment I had crept in through the kitchen window at McMurtrie's house pointed to the same conclusion.

I may appear stupid not to have seen through the doctor earlier, but after all a gang of professional spies is hardly the sort of thing one expects to run up against in a Devonshire village. A few years ago, indeed, I should have laughed at the idea of their existence anywhere outside the pages of a shilling shocker, but my three years in Dartmoor had led me to take a rather more generous view of what life can throw up in the way of scoundrels.

Whether they had killed Marks or not, I had little doubt now that they were wholly responsible for the attempt to murder Latimer. Though I had good evidence that when it came to the point the two gentlemen on Sheppey didn't stick at trifles, I could hardly fancy a couple of German Naval officers deliberately countenancing such methods. If they had, they certainly deserved the worst fate that even Mr. Gow could wish them.

Somehow or other my private interest in the affair seemed to have been temporarily forced into the background. I felt I was probably doing the best thing I could for myself in throwing in my lot with Latimer, but in any case his enthusiasm had got hold of me, and at all risks I was determined to stick to my side of the bargain. I knew that in her heart Joyce would have hated me to do otherwise.

My chief danger, as she had instantly seen, was the chance of Sonia betraying me to the police. The latter, who knew nothing of the part I was playing as a sort of unpaid bottle-washer to the Secret Service, would at once jump at the chance of arresting an escaped convict--especially such a well-advertised one as myself. However improbable Sonia's story might sound, they would at least be certain to take the trouble to investigate it.

On the other hand, of course Sonia might not go to the police at all, and even if she did, it was quite possible that Latimer would strike first and so give me the chance of clearing out.

Anyhow, forewarned as I was, I felt it would be an uncommonly bright policeman who succeeded in arresting me. In the day-time, so long as I kept a good look out, anything like a surprise attack was impossible, and after that night I made up my mind that I would sleep on the _Betty_. The only thing was, I should most certainly have to deprive myself of the luxury of a skipper. Useful as he was at taking letters into Tilbury, it would be decidedly embarra.s.sing to have him on board if I happened to arrive in a hurry on the beach with two perspiring detectives in hot pursuit.

At six o'clock, as there was still no sign of a visitor, I decided to walk over to the _Betty_ and tell Mr. Gow that he could treat himself to another holiday. It would only take me about half an hour, and in case McMurtrie turned up while I was away I could leave a message on the door to the effect that I should be back before seven.

I did this, pinning it up carefully with a drawing-tack and then after making sure that everything was secure I started off for the creek.

I found Mr. Gow in his usual restful att.i.tude, his head and shoulders sticking up out of the fo'c's'le hatch, and a large pipe protruding from his mouth. With the instincts of a true retainer he promptly removed the latter as soon as he heard my hail, and hoisting himself up on deck put off in the dinghy.

"I'm not coming aboard," I said. "I only walked over to tell you that you can have a couple of days ash.o.r.e. We shan't be using the boat till Sat.u.r.day or Sunday."

He thanked me and touched his cap (I could see he was beginning to think it was rather a soft job he had stumbled into), and then, with the air of some one breaking unpleasant tidings, he added: "Do you happen to know, sir, as we're clean out o' petrol?"

I didn't happen to know it, but under the circ.u.mstances it was information I was glad to acquire.

"Can you get me some--soon?" I asked.

He nodded. "I'll bring along a couple o' cans in the mornin', sir, and leave 'em aboard."

"Any news?" I asked.

"Well, sir, I seed the Dutchmen's launch goin' down this arternoon--travellin' proper they was too, same as when they swamped me. I suppose you ain't bin able to do nothin' about that matter not yet, sir?"

"I'm looking into it, Mr. Gow," I said. "I have a friend helping me, and between us I think we shall be able to get some satisfaction out of them. I shall probably have more to tell you on Sat.u.r.day."

With this answer he seemed quite content. "Well, I'll just run back aboard and get my bag, sir," he observed. "I reckon I'd better pull the dinghy up on top o' the bank when I done with her. If any o' them Tilbury folk should 'appen to come along they won't see 'er then--not among the long gra.s.s."

It was a sensible suggestion on the face of it, but in view of the fact that I might find it necessary to embark rather abruptly, I couldn't afford to risk any unnecessary delays.

"Don't bother about that tonight, Gow," I said. "Just drag her above high-water mark. It's quite possible I may be using her in the morning."

Having thus provided for my retreat in the case of an emergency, I returned to the hut by the usual route along the sea-front. I took the precaution of putting up my head and inspecting the place carefully before climbing over the sea-wall, but I might as well have saved myself the trouble. The marsh was quite deserted, and when I reached the hut I found my little notice still pinned to the door, and no trace of any one having paid me a visit in my absence.

I remained in the same state of splendid isolation for the rest of the evening. There was no difficulty about keeping watch, for as soon as the sun went down a large obliging moon appeared in the sky, lighting up the marsh and the Tilbury road almost as clearly as if it were day-time. I could have seen a rabbit a hundred yards off, let alone anything as big and obvious as a Scotland Yard detective.

At about one in the morning I turned in for a couple of hours' rest.

I felt that if Sonia had gone straight to the authorities they would have acted before this, while if she was sleeping on her wrath there was no reason I shouldn't do the same. I had given up any expectation of McMurtrie until the next morning.

I woke at half-past three, and resumed my vigil in the pure cool twilight of early dawn. I watched the sun rise over the river, and gradually climb up into a sky of pale blue and lemon that gave promise of another radiantly fine day. There was scarcely a breath of wind stirring, and everything was so deliciously quiet and peaceful that it almost seemed as if the events of the last three years were merely the memory of some particularly vivid nightmare.

"Almost," I say, for as a matter of fact I was never for a moment under any such pleasant delusion. If I had been, I should have had an early awakening, for at eight o'clock, just as I was thinking of routing out something in the nature of breakfast, I saw a little black dot advancing along the Tilbury road, which soon resolved itself into the figure of my faithful Charles.

He struck off across the marsh and came up to the hut, where I was standing at the door waiting for him.

"Two telegrams and a letter for you, sir," he said, producing them from his bag. "They came this morning, sir."

With an a.s.sumption of leisurely indifference that I was very far from feeling, I took them out of his hand. The letter was addressed in McMurtrie's writing, but I put it aside for a moment in favour of the two wires. The first was from Joyce.

"Saw L. late yesterday evening. He will act today. Agrees with my suggestion about the _Betty_ if necessary. J."

I thrust it into my pocket and opened the other.

"A copper come last nite and ask for you. He see Misses O."

For an instant I stared at this cryptic message in bewilderment; then suddenly the recollection of my final instructions to Gertie 'Uggins rushed into my mind.

So Sonia _had_ gone to the police, or had at least contrived to send them a message which served the same purpose. Their visit to Edith Terrace was probably explained by the fact that she had given them both addresses so as better to establish the truth of her story.

Anyhow the murder was out, and with a new and not unpleasant thrill of excitement I crushed up Gertie's wire in my hand and tore open McMurtrie's letter.

"DEAR MR. NICHOLSON,

"I have been away on business and have only just received your letter, otherwise I should have come to see you this afternoon. In the first place allow me to congratulate you most heartily on your success, of which personally I was never in any doubt.

"For the moment I have left the Hotel Russell, and am staying with some friends in Sheppey. I shall run up the river in their launch early tomorrow morning, as I believe there is a small creek close to the hut where we can put in.

"Please have a specimen of the powder ready, and if it is possible I should like you to arrange for an actual demonstration, as I shall have a friend with me who is already considerably interested in our little company, and would be prepared to put up further capital if convinced of the merits of your invention.

"You can expect us about high water, between half-past nine and ten.

"Your sincere friend,

"L.J. McMURTRIE."