Two tall men walked along a corridor two hundred feet below the Tower of London. Their footsteps raised echoes from the tiled floors and painted cement of the walls.

The man on the right was known only as J. A casual look at him would have suggested that he was a senior civil servant, nearing retirement age after many years of faithful and unobtrusive service. The Oxford accent, the erect carriage, and the flawless, understated tailoring of his dark gray suit all reinforced the impression.

The man on the left was named Richard Blade. He had always been harder to classify than J, and always would be. A dark man, one might have called him-dark hair, dark, closely trimmed beard, skin tanned almost to swarthiness. A wealthy man-he wore a custom-tailored suit, handmade brown shoes, a fine digital watch. A powerful man-under that suit was obviously an athlete's body, massively muscled and conditioned. If asked to guess about Richard Blade, the onlooker would have probably said, «A well-off amateur athlete and man about town.»

The onlooker would have been spectacularly wrong about both J and Richard Blade.

J had indeed served the British Crown faithfully and unobtrusively for many years. In espionage a man has to be faithful, and a man who isn't unobtrusive doesn't live very long. J was one of the century's great spymasters and head of the secret intelligence agency MI6. He had also reached an age where a normal man would have been at least thinking about retirement. But those who make distinguished careers in the dim shadowy world of espionage are seldom so normal.

Richard Blade was indeed a trained athlete, and not at all short of money. He'd been one of MI6's finest and deadliest field agents, picked by J himself when fresh out of Oxford. There was nothing of the amateur about him, and there never would be. He was a brilliant and formidable professional in a game more demanding and far deadlier than polo or tennis or steeple-chasing.

He was also unique in the whole world. He was the only living human being who could travel into other Dimensions and return safely. It was because of Blade's uniqueness that he and J were walking along the echoing corridor far below the Tower of London. At the end of the corridor lay a series of rooms, and in the last of those rooms stood an enormous computer. That computer was the creation of Lord Leighton, who had the most brilliant mind and usually the worst temper among all of Britain's scientists. Richard Blade's brain would be linked to that computer, so that they formed a single circuit. Then Lord Leighton would pull a red master switch, activating that circuit, and Richard Blade would whirl off into-somewhere else.

They called that «somewhere else» Dimension X. When the great computer had finished twisting Blade's brain and senses, he saw and smelled somewhere else, heard and felt somewhere else, fought and moved somewhere else. Somehow he always survived and came back alive, sane, and reasonably healthy, to tell of what he had done and seen in the unknown. He was the only living person who could do that, in spite of all the efforts made to find others.

There was much more to what had now become Project Dimension X than simply giving Richard Blade a chance for one incredible adventure after another. Out there in Dimension X lay vast resources of all the things that Britain so desperately needed-land, metals, knowledge. Blade had gone out twenty-three times and come back twenty-three times, but he'd never been able to bring back more than tantalizing samples or hints of the wealth of Dimension X. In spite of all the money, work, thought, and good intentions that had gone into it, the Project still seemed to be doing very little except giving Blade those exotic adventures.

This was becoming a problem, one that would rapidly get worse if things didn't change soon. It was this problem that Blade and J were discussing as they walked down the corridor.

«The total value of what you've brought back in gold and jewels and the like is adding up quite admirably,» said J. «The grand total is now over three million pounds.»

«That's not enough to cover the whole cost of the Project, is it?» asked Blade. He knew that he should take more interest in the budgetary and administrative side of the Project. He had never been an office type, though, or able to concern himself very much with even the most essential paperwork details.

«No. The total investment in the Project since we started is about eleven million. But what you've brought back has helped keep us within what the Prime Minister's Special Fund can absorb.»

«I imagine the Prime Minister is happy about that.»

«Not happy,» said J. «Not at the moment. He's reasonably satisfied with the financial end of the affair, and otherwise-well, Leighton's submitted another report.»

«And put his foot in it again?» The scientist had a long-standing habit of conceiving and proposing large additions to the Project and its budget at the drop of a hat, without bothering in the least about minor details of trained manpower or financing.

«If you mean, has Lord Leighton made some new and expensive proposals in his report-yes, he has. This time he's sat down and drawn up a comprehensive scheme for the Project for the next three years, covering long-lead time purchases, contingency planning, everything. I hadn't imagined that he had such a grasp of planning techniques.»

J sounded genuinely impressed, rather than exasperated as he usually was by Lord Leighton's proposals. «You sound as though you're supporting him, sir,» said Blade.

«I am,» said J. «Or at least I would be, if it would do any good. Leighton's done a fine job. He hasn't asked for anything we shouldn't have had years ago.»

Blade hesitated, then fired the decisive question. «How much will it all cost?»

«Four million.»

Blade grimaced. «I don't imagine we have much chance of getting that.»

«None whatever. It can't possibly come out of the Special Fund, and as for getting a regular appropriation-well, you know as well as I do what the chances are of that, even if it were safe.»

Blade nodded silently. The Prime Minister's Special Fund was the only source of money for the Project where no questions would be asked. In Parliament there always had been and always would be those who would question an unidentified expense of five pounds if they thought it would score them political points. With four million pounds they would have a field day, and the security of Project Dimension X would never survive.

It had to survive, though. No other nation knew the secret of inter-Dimensional travel. No other nation appeared to even know that the British had discovered it. Things had to stay this way as long as possible. What the Russians might do if they could tap the secrets of Dimension X was something to give the calmest of men nightmares.

«Besides,» J went on, «Parliament wouldn't be inclined to come up with four million pounds for any scientific project these days, unless it's got some obvious value.» Frustration and a strained temper sounded in J's voice as he continued. «Meanwhile, everybody's moving on ahead of us in a dozen fields. Atomic power-the French are putting breeder reactors into service. Electronics-the Japanese have made half a dozen breakthroughs in superconductors. Genetics-in genetics, we've had reports that the Russians are on the point of cracking the codes for direct genetic manipulation.»

«I thought that had already been done,» said Blade.

«With bacteria, yes. But this report mentioned work with higher animals, at least up to the level of fish. Of course the- results will come more slowly with larger, slower-breeding animals-until they get cloning perfected. So we may not have to worry for a few years. But-imagine a swarm of mutated and cloned sharks let loose as a terror weapon, or to form a submarine detection network?»