An introductory note seems called for to explain to the reader the origin of the following strange document, which I have received from a friend with a view to publication. The author has given it the form of a letter to myself, and he signs himself with his nickname, "Cass," which is an abbreviation of Cassandra. I have seldom met Cass since we were undergraduates together at Oxford before the war of 1914. Even in those days he was addicted to lurid forebodings, hence his nickname.My last meeting with him was in one of the great London blitzes of 1941, when he reminded me that he had long ago prophesied the end of civilization in world-wide fire. The Battle of London, he affirmed, was the beginning of the long-drawn-out disaster.Cass will not, I am sure, mind my saying that he always seemed to us a bit crazy: but he certainly had a queer knack of prophesy, and though we thought him sometimes curiously unable to understand the springs of his own behaviour, he had a remarkable gift of insight into the minds of others. This enabled him to help some of us to straighten out our tangles, and I for one owe him a debt of deep gratitude. He saw me heading for a most disastrous love affair, and by magic (no other word seems adequate) he opened my eyes to the folly of it. It is for this reason that I feel bound to carry out his request to publish the following statement. I cannot myself vouch for its truth. Cass knows very well that I am an inveterate sceptic about all his fantastic ideas. It was on this account that he invented my nickname. "Thos," which most of my Oxford friends adopted. "Thos," of course, is an abbreviation for Thomas, and refers to the "doubting Thomas" of the New Testament.Cass, I feel confident, is sufficiently detached and sane to realize that what is veridical for him may be sheer extravagance for others, who have no direct experience by which to judge his claims. But if I refrain from believing, I also refrain from disbelieving. Too often in the past I have known his wild prophesies come true.The head of the following bulky letter bears the address of a well-known mental home."THOS."