“To what extent the mania so produced is homicidal remains to be proved; the gas is rare and difficult to procure, so that hitherto analysis has not been attempted. My own theory is that the subject remains harmless provided that, whilst under the mysterious influence, he does not encounter any person distasteful to him. Thus, Seager may have met his death at the hands of some tramp who had been turned away from the house.
“As to the symptoms: they seem to be quite unvarying. The subject strips, contorts his face out of all semblance to humanity (and always in a particular fashion) and crawls, lizard-like upon the ground, with the head held low, in an attitude of listening. That it is possible so to contort the face as to render it unrecognizable is seen in some cases of angina pectoris, of course.
“The subject apparently returns to the spot from whence he started and sinks into profound sleep, as is seen in some cases of somnambulism; and—like the somnambulist, again—he acquires incredible agility. How you yourself came, twice, under the influence of the vapour, is easily explained. The first time—when the housekeeper saw you—you had actually been in bed; and the second time, as you have told me, you had gone upstairs, undressed, and then slipped on your dressing-gown in order to complete some work in the study. Instead of completing the work, you dozed in your chair—and we know what followed! In the case of—Mrs. Dale....”
“God! Addison,” said the Major huskily, and stood up, clutching the chair-arms—“Addison! You are trying to tell me that—what I saw was ... Marjorie!...”
I nodded gravely.
“Without letting her suspect my reason for making the inquiries, I learnt that on that last night at Low Fennel, feeling dreadfully lonely and frightened, she determined to run along to the new wing—which seemed a safer place—and to wait in your room until you came up. She fell asleep, and....”
“Addison ... can a mere ‘vapour’ produce such....”
“You mean, is the vapour directed or animated, by some discarnate, evil intelligence? My dear Major, you are taking us back to the theory of Elemental spirits, and I blankly refuse to follow you!”