"Mannering is five feet eleven and a quarter in his socks," I remarked.

"Secondly, that his hair was black. Thirdly, that the nails of the right hand, with which he took his plunder, were bitten to the quick."

"The identification becomes nearly perfect," I interrupted.

"Fourthly, that the car was originally a two-seated car, with a tonneau body, but that the seat had been set back, and the bonnet was enclosed by metal plates shaped into the form of the bow of a canoe, and bolted together in a manner which gave the impression that they might easily be removed. Why," continued the detective, "I did not think of so obvious a solution of the Pirate's mysterious disappearances before I cannot imagine. It is the trick the black flag merchants have practised since the days of Captain Kidd."

I was silent. I could only wonder at my own blindness. Then an excuse occurred to me.

"After all," I remarked, "we only met him in the dark."

CHAPTER XXI

WE PLAN AN AMBUSH

FORREST had just concluded his story when the lights of Thetford gleamed in our eyes. The time was 12.30. The last train was gone. The inhabitants were all in bed, and there we were, stranded with a broken car, and no means of putting it right. Forrest would not despair, however, and after some difficulty we managed, with the a.s.sistance of the local police, to knock up a man who was locally reputed to know all about motors. He was a little surly at first, but the inducement I offered him to make an attempt to put the transmission right, was sufficient to dissipate his very natural disgust at being disturbed in his beauty sleep. Fortunately his local reputation had reasonable foundation. He was a very capable mechanician, and the way he set about the job gave me great hopes that the car would run as well as ever when he had done with it. And my expectations were gratified. In less than an hour he had completed the repairs. I paid him and asked him to remain up for ten minutes in case we had another breakdown, telling him that after that period had elapsed, he would be at liberty to return to his bed.

Whether he waited the ten minutes or not I do not know, for by that time we were halfway to Newmarket, flying through the darkness at a pace which two months previously I would not have dared venture upon in broad daylight. And right onward to St. Albans, we kept it up, reaching the ancient town just as the birds began to twitter in the hedges at the first grey light of early dawn. At St. Albans we stopped at the police-station. A man was waiting at the door.

"Any news?" asked Forrest.

The man shook his head.

"You know where to bring it?" asked my companion.

The man nodded.

"Let us get on home," said Forrest to me.

As I wheeled my vehicle into my yard I thought I should drop. The strain of that rush through the night, expecting every moment that something would give way, had been tremendous, and the moment the tension was relaxed I shook like an aspen leaf. When I tried to get in at my own door I found I could not fit the latch-key, and was obliged to hand it to the detective. He saw what was the matter with me, and the moment we were inside, he led the way to my study, thrust me down into a chair and mixed me a whisky-and-soda. I was never more grateful for a drink in my life. It pulled me together, and in less time than I had conceived possible, I felt as if I could have managed another seventy-five miles without a halt.

The moment he saw my nerves were steady again, Forrest proposed that we should get something to eat. I declared that I did not want anything.

"When you haven't time for sleep, the next best thing is to feed well if you want to keep fit," he remarked. "Besides, I am as hungry as a hunter has a right to be."

"That settles it," I laughed. "We shall have to forage for ourselves.

The servants are all asleep."

We found our way to the larder and made a hearty meal on a cold pie we found there; and directly we had finished, we set out forthwith in the direction of Mannering's home. As soon as we arrived opposite the house, Forrest paused and gave a low whistle. It was answered immediately by a man dressed as a labourer, who made his appearance from behind the hedge opposite the house.

"Any one been here to-night, Laver?" asked Forrest.

"No one," the man answered. "The servants turned in about ten after locking up. No signs of any one about the place since."

"That's all right," grunted Forrest. "We shall be ready for him when he does come. Have you got the tools?"

The man was proceeding to scramble through the hedge when Forrest checked him.

"Better stay where you are," he advised. "Keep out of sight, and if I whistle, come at once."

"All right, sir," replied the man, as he handed through a gap in the hedge a small chamois leather bag.

I had no idea as to what steps Forrest proposed to adopt in order to effect the arrest, so I asked him, and he explained briefly his plan of campaign.

"One can see," he remarked, "that Mannering feels so confident of the completeness of his disguise that he will have no hesitation about returning. I am reckoning, too, upon there being an element of truth in the story he has told you about the construction of his motor, in which case his own workshop would be the only place where he would be able to refill his tank. We shall be able to decide that point in a very few minutes. If we do find any plant for the production of liquid gases, we can count upon catching our man within a very few hours."

"Unless he smells a rat, and makes for some convenient port and gets out of the country," I remarked.

"That eventuality is provided against," remarked the detective. "His description is in the hands of the police at every port in the kingdom, and even if he changes the colour of his hair, I don't think he will manage to get away. What I propose is, that we shall remain concealed in his coach-house and await his return."

"How are we going to get in?" I inquired.

Forrest took a bunch of skeleton keys from the bag Laver had handed to him and dangled them before his eyes.

"There's not a burglar in the kingdom is better provided," he remarked, and set to work upon the lock forthwith.

The lock was an ordinary one, and his efforts were speedily successful.

The door swung open, and we entered eagerly a bare, stone-paved coach-house. Opposite the door by which we had entered from the road was a similar door, which gave upon the inner yard. On the left, a large sliding door had been fixed in place of the wall which had divided the coach-house from the stables. Relocking the door by which we had entered, Forrest led the way to the door on the left. It was unfastened, and as it swung back a cry of amazement sprang to my lips.

"Hush--sh--sh!" said the detective warningly.

But I could not have repressed the cry, for there before me stood a replica of the car I had seen on two occasions. There was only one point of difference at first apparent. The pirate car had been black. This one was built of aluminium and gleamed silvery white. But although the lines were very similar, I soon came to the conclusion that the car we saw before us was not the one which the Pirate had used when engaged upon his nefarious work. One glance at the tyres convinced me that they had never been upon the road, and I fancied that the wheels were smaller and the lines of the body finer altogether. I pointed these things out to Forrest, who, while agreeing that this particular car could not have been the one which had been responsible for holding up the "August Personage" on the previous day, would not commit himself further.

We did not spend much time upon a close examination of the car, for the other contents of the building claimed our attention. We found ourselves in a long workshop. There were no windows in the walls, but the place was amply illuminated by a skylight which ran along nearly the whole length of the northern slope of the roof. On the right of the large door by which we had entered the inner shop was a small room, which had probably once served as a harness-room, for through this another door gave on to the yard, though this exit was evidently never used, for the door was fixed by screws. The contents were a couple of broken chairs, and some coats and rugs hung upon hooks upon the walls, together with a miscellaneous a.s.sortment of odds and ends upon a shelf. I gave merely a cursory glance at the contents of this apartment, for my attention had been attracted by a plant of machinery, which occupied the far end of the large room. As it happened, I had once had an opportunity of inspecting the laboratory of the Royal Inst.i.tution, and I recognized at once that Mannering had set up an installation for the preparation of some one or other of the liquid gases. Without this experience, I doubt whether it would have been possible for me to guess even the purpose for which the plant had been devised. As it was, I had no hesitation in discovering the receiver into which the liquid gas was distilled; and when I let a little of the liquid with which it was filled run into a gla.s.s which I found handy, and saw the air fall in a shower of tiny snow-flakes as the stuff evaporated, I knew that Mannering had told me the exact truth when he had informed me that liquid hydrogen supplied the power for his new car.

Once satisfied on this point, I examined the other contents of the place. I do not think there is any need to particularize all that we discovered, even if my memory served me. Practically the workshop contained a sufficient engineering equipment to build such a car as stood in the centre, though I judged that there was no convenience for the forging of the parts of the motor.

Still, as I pointed out to Forrest, there was nothing in all these discoveries to negative the truth of the story Mannering had told me about his being engaged in building a car which should serve to outpace the Pirate car, but he would not listen to any theorising on the subject.

"He can tell that story to the jury," he said, as he significantly drew a pair of handcuffs from his pocket and clinked them together. Then he proceeded to investigate the contents of the harness-room, while I went back to the new car and began a careful examination of the engines. The whole mechanism was, however, so novel to me, that I could only surmise as to the method of its working. I did notice, however, that the driving and steering gear varied very little from that of my own car, so far as it was controlled by the levers and wheel, while the breaks seemed to be particularly powerful. There was only seating accommodation for two, and judging from the size of the tank which was fitted behind the seat, I judged that Mannering contemplated runs over distances which would make large demands upon his supply of liquid gas.

At the moment I made this discovery, I heard Forrest call to me in an excited whisper, and going across to him, I found him contemplating with keen interest a dirty piece of rope.

"Look here, Sutgrove," he said; "this is the piece of cord with which he trussed me up on the occasion when he dropped me into the pond. Compare it with this"--he kicked a coil which lay at his feet--"and tell me if they are not identical."

I examined them both, and came to the conclusion that Forrest was correct in his supposition. Next, mounting one of the chairs, he proceeded to rummage amongst the rubbish piled on the shelf. A moment later he observed triumphantly, albeit in subdued tones, "Another piece of evidence," and descending from his perch, he handed me a box of cartridges. A glance at the label had apparently been enough, nevertheless, to make sure, he searched again in his pocket, and produced the bullet which had proved fatal to the poor victim at Towcester. He compared it with one of the cartridges, and gave a grunt of content. "I fancy we shall soon obtain sufficient evidence to hang him," he murmured. Then a shadow crossed his face. "What an infernal dunderhead I have been not to suspect him before," he said, and turning impatiently away, he replaced the box of cartridges on the shelf, before renewing his systematic examination of the rest of the contents of the room. The search revealed nothing further, and at length he desisted.

All the while we were keenly on the alert to detect any sound which should tell us of the approach of Mannering's car. But the minutes pa.s.sed and grew into hours without a sign. It must have been about five in the morning when we had entered the coach-house, and when I saw by my watch that it was nearly ten, I began to think that in some way or another Mannering had got warning of the danger that threatened him. I suggested to Forrest that we might as well leave our hiding-place, but he would not hear of it.

"I don't leave this building except in his company, unless I hear that he has been captured elsewhere," he declared obstinately. "At the same time, don't let me detain you."

I wanted badly to see Evie, whom I thought might be getting anxious concerning me; but I hardly liked the idea of leaving Forrest to tackle Mannering alone if he should return. However, my first desire triumphed, so I persuaded Forrest to let me out of the door, promising to return within as short a time as I could manage.

I hurried first to the Colonel's house, and had a brief interview with the dear girl, telling her what had happened and what was likely to happen in the near future. Next, I went to my own place, and had a basket packed with a plentiful luncheon, not forgetting to provide a couple of bottles of champagne, and thus provided I returned to the coach-house after an absence of less than an hour.