the poison into his
lungs through hours of sleep, producing--nightmare. Science has by no
means analyzed all the possibilities of such phenomena."

"Nightmare!" I cried. "Do you mean to account by nightmare for the wide
and repeated experiences that twice brought me to the verge of death?
And Desire? What of her knowledge of that same nightmare? What of the
legend of her family so exactly coinciding with all I felt? And why did
not Phillida and Ethan suffer the nightmare with me?"

He held up a lean hand.

"Gently, gently, Roger! Consider that of all the household you alone
slept in the side of the house toward the lake. I know that you always
have your windows open day and night--a habit that used to cause great
annoyance to your Aunt Caroline when you were a boy. Thus you were
exposed to the full effect of the water gases. That you did not feel the
effects every night I attribute to differences in the wind, that from
some directions would blow the fumes away from the house, thus relieving
you. I gather from your account that the phenomena were most pronounced
in close, foggy weather, when the poisonous air was atmospherically held
down to the earth. You have spoken of miasmic mists that hung below the
level of the tree-tops. When Mr. Vere experienced a similar unease and
depression, he was on the shore of the lake at dawn after precisely such
a close, foggy night as I have described as most dangerous. The symptoms
confirm this theory. You say you awakened on each occasion with a sense
of suffocation. Your heart labored, your limbs were cold and mind
unnaturally depressed, owing to slow circulation of the blood. You were
a man asphyxiated. After each attack you were more sensitive to the
next, as a malaria patient grows worse if he remains in the swamp
districts. It is remarkable that you did not guess the truth from the
smell of decaying vegetation and stagnant damp which you admit
accompanied the seizures! However, you did not; and in your condition
the last three days of continuous fog brought on two attacks that nearly
proved fatal. Now as to the character of your hallucinations, and their
agreement with the young lady's ideas. That is a trifle more involved
discussion, yet simple, simple!"

He put the tips of his fingers together and surveyed us with the benign
condescension of one instructing a class of small children.

"The first night that you passed in your newly purchased house, Roger,
you accidentally