Richard said softly, «The Tower of London frowned dreadful over Jerusalem.»

«What's that supposed to mean?» J demanded.

«It's poetry,» Blade explained. «William Blake wrote those lines way back in the eighteenth century. He rather caught the spirit of this place, don't you think?» Richard had memorized an astonishing amount of classic verse at Oxford, and had a habit of quoting it at the most unlikely times. «Blood! Horror! Doom! That's what we think of when we hear about the Tower of London, and small wonder. Some of the grandest rascals in English history passed through this old Watergate on their way to torture, imprisonment or beheading. That's why it's called the Traitor's Gate.»

J thought, The Traitor's Gate! How apt. Two Russian spies have passed through here in very recent history and penetrated to the heart of the secret project, in spite of all our fanatic security precautions. Neither had returned alive to reveal what went on there, but next time…

J shuddered.

«There you are, sir,» the tall man said. The gate opened with a creak. J and Richard Blade stepped inside.

The Special Services men locked them in and vanished into the fog, returning to their posts. In the yellow light from a bare electric bulb in the ceiling, Blade and J proceeded onward, locating the almost invisible secret door that led into a long, dim, damp tunnel, into a maze of sub basements, and finally to the familiar door of the elevator.

J pressed the elevator button, aware that the button was photographing his thumbprint as he did so. Far below a computer would compare his print with that of everyone who had a security clearance for the project and, deciding that J was «all right,» would, in a few seconds, send up the elevator.