It was Rex who broke the unhappy silence. “If we’re not the world’s prize suckers,” he declared bitterly, “I’d like to know who are!” And he began to roar with such hearty laughter that the Duke and Simon could not forbear joining in.

“This is no laughing matter.” De Richleau shook his head. “What the devil are we to do now?”

“Walk,” said Simon, the ever practical, and in truth it was the only thing they could do.

“Good for you,” Van Ryn exclaimed, patting him on the shoulder with one large hand while with the other he picked up the rifle and the strap of Simon’s rucksack. His cheerful face showed no hint of his quick realization that the pace of the party must be that of the slowest member, or his anxiety as to how many hours it would be before Simon’s frail physique gave out under the strain. He only added: “Come on, let’s beat it.”

De Richleau collected his things more slowly. “Yes,” he agreed, “we must walk — at least, until we can buy or steal horses. But which way?”

“To Romanovsk,” said Rex. “That way’s as easy as any other, and I’d sure like to have a cut at those jewels before I go back home.”

“As you wish.” The Duke gently removed the ash from his cigar. “We have had no time to tell you our own adventures, Rex, but there is one little episode which makes me particularly anxious to avoid capture.”

“Give me that sack and let’s hear the worst,” Rex remarked casually, as he slung the Duke’s rucksack over his shoulder next to Simon’s.

“My dear fellow, you can’t carry two!” De Richleau protested, “particularly after having driven all night.”

“I certainly can,” Rex assured him. “I’d carry a grand piano if I felt that way, but I’ll give ’em back quick enough if I get tired, don’t you worry. Let’s hear just how you blotted your copybook!”

“An agent of the Ogpu followed us as far as Sverdlovsk. If his body should chance to be discovered, and we are captured, it might prove a little difficult to explain,” said the Duke mildly.

Rex whistled. “You gave him the works, eh? Great stuff; but if that’s so, they’ll not be content to put us behind the bars this time; it’ll be we three for the high jump!”

“We — er — hid the body,” Simon remarked; “if we’re lucky they won’t find it till the spring.”

Side by side they walked down the cart-track, and turning into the road set their faces to the north. “I’ll say we’re lucky today anyhow,” Van Ryn threw out; “if it had snowed last night we’d not make a mile an hour without snowshoes, as it is the going won’t be too bad on the frozen crust.”

They trudged on for a long time in silence; there was no traffic on the long, empty road, and the intense stillness was only broken by a hissing “plop”, as a load of snow slid from the weighted branches of the firs, and the steady drip, drip, as the hot sun melted the icicles hanging from the trees.

It must have been about half past nine when Rex suddenly stopped in his tracks — he gripped the others tightly, each by an arm, as he exclaimed: “Listen — what’s that?”

A faint hum came to their ears from the westward. “’Plane,” said Simon, quickly. Even as he spoke Rex had run them both into the cover of the trees at the roadside.

“It’s a ’plane all right,” he agreed, “but that engine’s like no other that I’ve ever heard — and I know quite a considerable piece about aeroplane engines.”

All three craned their necks to the sky from the cover of the larches — the deep, booming note grew louder, and a moment later the ’plane came in sight. It was a small, beetle-shaped affair, flying low and at very high speed; it turned north when it was over the road, and passed over their heads with a great roar of engines. In a few seconds it was out of sight, and in a few minutes out of hearing.

“The hunt is up, my friends,” laughed the Duke, a little grimly. “These will be more difficult to throw off the trail than bloodhounds.”

“Somehow, I never thought of being chased with ’planes,” Rex admitted. “That certainly puts us in some predicament!”

“We must stick to the forest,” Simon answered. “Follow the road as long as there are trees, and leave it when there aren’t.”

As they journeyed on other ’planes came over; that it was not the same one going backwards and forwards was certain — since the numbers on each were different. Each time one came over Rex strained to catch a glimpse of the design, so different to anything he had seen before. The others cursed the necessity of stopping every twenty minutes, and often having to make long detours to keep under cover when the trees left the road.

Simon talked little. He was not used to exercise, and knew that if he were to come through he must husband all his energy. De Richleau, in spite of the fact that he was far older than either of the others, walked briskly. It seemed that in this new adventure he had regained something of the vitality of his earlier years; even if he was a little out of training, his body was free of any superfluous flesh, and his tough sinews were rapidly regaining their elasticity.

It was Van Ryn who kept up the spirits of the party. Two months in prison — far from quelling his natural exuberance — seemed to have made him relish his freedom all the more. He told them of his capture when hidden in a coal truck on the military train from Turinsk to Tobolsk — of how he had used the lumps of coal for missiles when they had tried to arrest him. There must have been quite a number of sore heads and aching limbs among that detachment of Red Guards on the following morning, but in the end he’d had to throw in his hand; being sniped from four different angles with the snipers a hundred yards away was no fun for a man only armed with lumps of coal — however big that man happened to be.

Then De Richleau gave an account of his and Simon’s activities since their arrival in Russia.

Simon was thinking of Valeria Petrovna — would he ever again, he wondered, behold her wonderful exotic beauty — touch the warm, golden softness of her skin, or feel her faintly perfumed breath on his cheek. Never would he forget those marvellous nights in Moscow, with a million stars shining in the frosty darkness from her window that overlooked the Moskawa River. It seemed absurd to think that he had only spent a week in Moscow. His well-ordered office in London, with its quiet, efficient routine, its telephones and typists — all seemed incredibly remote, like people and things in some former life. What would his able, unimaginative partners think if they could see him now? An accessary to a murder — on a forced march to escape capture by the police — and going where? After some absurd treasure buried by some mad prince. He gave one of his quick, sideways glances at his two companions. Surely the whole thing was a dream — a nightmare — and he would wake up in his comfortable bedroom at his club! Even as he turned his head the slight pressure of Valeria Petrovna’s ikon against his chest assured him that it was all very real indeed.

They had halted in sight of the first houses of a small village. De Richleau and Van Ryn began to discuss the advisability of raiding some lonely farmhouse for horses and a sleigh; the Duke was for an immediate attempt to obtain them at all costs — by purchase, if possible, and if not, by force.

Van Ryn was against this — he argued that if they were to get a sleigh now, in the early afternoon, they would almost certainly be spotted by the aeroplanes, since they would be forced to remain on the road. By comparing a big sweep in the river with their map, he pointed out that it could not be more than five miles to Romanovsk, so he proposed that they should stick to the woods and walk the remaining distance. By nightfall they would be safe from aeroplane observation. He was willing enough to beat up any farm if need be — but let it be after dark!

Simon sided with Rex, and so it was settled; they made a wide detour, leaving the village on their right. The forest was of larch and pine, with little undergrowth, and in its shelter they found walking easier, for the heat of the sun had started to thaw the frozen crust of the road, and progress on it had become increasingly difficult.

It was during this detour that they saw the first flight of big ’planes. They were crossing a wide clearing at the time, and dodged hastily back among the trees. Six giant ’planes, flying in perfect formation, and at less than a thousand feet, roared over their heads — they were followed by six more, and yet another six, in quick succession.

De Richleau looked at the other two. “This is very strange; the small ’planes which we saw all the morning may have been searching for us, but we can hardly suppose that they would turn out flights of bombers on our account!”

“Must be an air-park somewhere around,” suggested Rex.

“Jack Straw told us to keep our eyes open for anything military up this way,” nodded Simon.

“If it is,” drawled Rex, “it ’ud sure interest the secret service folks in Washington.”

“An air-park,” murmured the Duke. “And you say, Rex, that these ’planes are of a completely different type to those generally used in Europe and America?”

“Sure, the wings are set at a different angle, and they’re shorter — you can see how much more like dickybirds they look than ours.”

They continued their way through the forest, but after they saw the first squadron of big bombers, the hum of innumerable aeroplanes was always in the background, loud or faint, breaking the silence of the afternoon.

In threes or in sixes, or singly, the sky was rarely free of them as they swooped or hovered, practising their evolutions. They were of three distinct types — the single-seater scouts, the big bombers, and what Rex declared to be a four-seater fighting machine. All of them were monoplanes, but fitted with a queer upper structure of two slanting blades, which formed a smaller pair of wings — these, Rex thought, were a new form of helicopter, to enable them to land in a confined space.

They had just breasted a slight rise, when they first saw the fence; it stretched away on either hand, some fifty yards in front of them, the height of a man, and formed of six strands of copper wire, which shone brightly in the sunlight — the wires stretched taut throughout steel uprights. It looked innocent enough, but De Richleau, at least, had seen fences of that type before — on the enemy frontiers during the War.

As they walked up to it, he laid his hand on Simon’s arm: “Be careful, it is almost certain to be electrified — it would be instant death to touch it!”

Rex pointed to a dead ermine that lay a few feet away. “Sure thing, that poor feller crashed it. I guess he never knew what hit him. I’ll say they’re mighty keen to keep people out of their backyard in these parts.”

For some time they walked parallel to the fence, which ran roughly north and south. After they had covered nearly half a mile Rex halted suddenly; Simon stopped too, having, at the same moment, caught sight of a grey figure among the trees. De Richleau instinctively followed their movement as they flung themselves on the ground. He looked at them questioningly.

“Sentry,” whispered Simon, pointing. And there, between the trees, on the other side of the wire, they could make out the form of a Red Guard. He was standing quite still, with his back to them, as he leant on his rifle. He was a little man, and his overcoat was too big for him; his hat was thrust on the back of his head, and his attitude bespoke dejection. He was a pitiful, rather than a frightening, figure — nevertheless they had no desire to be seen, and crept stealthily back until they were well out of view.

“God-forsaken job,” said Simon, as they proceeded on their way again. “Standing in the snow all day — guarding an air-park a thousand miles from anywhere, that no one knows exists!”

“That’s just why it’s so important,” remarked the Duke. “Nobody knows it exists!” Even as he spoke they came out of the belt of trees, the ground sloped sharply away to their left front — a wonderful panorama was spread in front of them.

The electric fence came out of the wood and ran down the hill a quarter of a mile to their left; beyond it stretched a great open amphitheatre of at least three miles across in each direction, the whole surrounded by the dark ring of forest.

Line upon line of aeroplane hangars lay spread below them — squadron after squadron of ’planes: bombers, fighters, scouts, looking like toys in the distance, their wings flashing silver in the afternoon sun. Row upon row of hutments and barracks, offices, and repair sheds. All the time little flights of ’planes rose and descended with perfect precision on the numerous landing grounds. In every part of the park some sort of activity was going forward — tractors were pulling ’planes in and out of hangars, little groups of soldiers were drilling or being marched from place to place; for many minutes the friends stood silent, watching this amazing spectacle.

“The Forbidden Territory,” Simon laughed, suddenly.

De Richleau nodded. “Yes, this is the secret they are so anxious to preserve — it must have been in order to create this gigantic air-camp that they finished the railway to Tobolsk, and put the road we came on last night in such good repair.”

“I reckon Jack Straw ’ud like to give this place the once-over,” said Rex.

“He’s given us the name of Colonel Marsden, at the Thatched House Club, in London. If we get through we must let him know of this,” De Richleau replied, thoughtfully. “How many ’planes do you think there are, Rex?”

“All of a hundred and fifty squadrons — two hundred, maybe, just take a look at those hangars — it’s impossible to count.”

“Well, now, I’ll tell you,” said Simon, quietly. “I never did believe what they say in Moscow about being frightened of a combined attack by the capitalist countries — they’re out to conquer us — that’s a certainty; I wonder how they feed this lot — the road was empty, and we’ve never been more than a mile from the local railway — yet we haven’t heard a single train go by!”

“Can’t you see?” Rex extended a long arm. “On the far side there, they’ve rail-trucks and engines — that little one-eyed decavil that runs by the river couldn’t supply five per cent of this outfit — they’ve scrapped it, and built a new one direct from Tobolsk through the forest. I’ll say it — ”

They were so interested that they had not noticed the approach of soft footsteps, deadened by the snow. Suddenly a voice behind them said, quietly:

“A dangerous secret for foreigners to know.”