If man can measure the amount of heat radiated by a candle at a distance of a mile, if he can prise open the oyster of the atom, it is only a matter of time before he will hear the voices of the past talking in the present.

Dogs have been known to return home hundreds of miles across country; pigeons fly homeward across the seas. Animals can smell what man cannot smell, and hear sounds that man cannot hear.

The human brain is found to emit wireless waves; if it can emit surely it can receive.

The scientific explanation of the working of the refined senses, of instincts, and of the brain, is writ large inside a deep scientific tome of which this generation is now opening the introducory pages.

Certain of man's senses have been dulled. One of them is the ability to appreciate consciously the proximity of fellow beings in the present, not to mention out of the past, without the aid of the simpler senses which remain man's standby -- sight and hearing and the nervous system.

Yet, dulled as the senses have been, something remains; an inchoate attribute by which man can sense vaguely what he commonly calls 'atmosphere'. Undoubtedly, much that provides the reaction in human beings which is often loosely termed the sixth sense, comes into the brain subconsciously through the other senses. The eyes, particularly, will take in much more than is consciously registered by the brain and will perform unconscious permutations and combinations with memories much like a calculating machine. At the same time, almost certainly, this other indefinable attribute reacts within the brain.

Colditz had an atmosphere. Naturally a castle that had stood for centuries would. But it was not the atmosphere of antiquity, of the passage of history within its walls that struck every new arrival upon entering the courtyard.

Colditz had more recently been a lunatic asylum. There was a weird, bleak and depressing air about the place which struck the newcomer so forcibly that he knew, without being told, that the Castle must have been filled at one time by a great sadness.

It was not the place to encourage a sane outlook upon life. The high, dun coloured walls surrounding the tiny cobbled yard; the barred windows -- even those opening on the yard were barred; the steep roofs which hung precipitously overhead; the endless clack-clack of wooden sabots; the cacophony of voices in different languages and musical instruments in different keys, were not calculated to breed contentment or resignation. As a lunatic asylum it had never been a sanatorium where insanity might hope to be cured. It could only have been a home for incurables and a dungeon for the violent.

Into this prison the Germans threw the men who, of all the prisoners of war in Germany, were the most likely to chafe and strain and pine under the stifling confinement of its oppressive walls. Those who had found resignation were not for Colditz. Those who had broken their chains and would continue to do so, filtered into the Castle.

Colditz was a fruitful breeding ground for frustration and might easily become a prison full of mentally unbalanced men.