It happened late in the evening, and before he went into the laboratory he uttered such strange words over the sleeping child that Frau Schimmel, who was watching beside it, was frightened, especially as Schimmel had not been called to aid the doctor, and what might happen to the distraught man, if he were left to work alone, passed in gloomy visions before the old lady. So she concealed herself behind the bellows that were attached to the furnace, and there she was witness of events that sent cold shivers down her back whenever she thought of them. In his best holiday costume of black velvet puffed with silk he entered the laboratory, holding himself very erect. The high, arched room was only dimly lighted by a hanging-lamp, but when Frau Schimmel heard his steps she shrank together till, as she fancied, she must have become smaller and less easily discoverable. What she feared was that he might start the furnace and she should be obliged to reveal herself because of the heat. But to her great relief he walked straight into the middle of the laboratory and stopped directly under the lamp, which was suspended from the point where the ribs of the vaulting intersected. There he waved a fresh laurel branch towards every side of the room and called out the same words and names that he had murmured by the bed-side of his son, only louder and more imperiously. To the listener it was perfectly clear that this was an invocation of spirits, and her knees trembled under her, and her teeth chattered so audibly that she feared he must hear her. Though she closed her eyes tightly in order not to see the hellish brood that was about to pervade that Christian house, fearing that she might be strangled by them or go mad; yet the unholy creatures must have entered the laboratory obedient to their master's call for she distinctly heard him greet one of them solemnly. As she did not smell any sulphur fumes nor see any dancing flames when she peeped out from under her half-closed lids, she gathered sufficient courage to look about her. But she saw nothing save the doctor on his knees talking into the corner of the laboratory, where there was nothing but the broom with which she had swept the stone floor that morning, and the shabby old brown peruke that Herr Schimmel was in the habit of putting on in the winter when he crossed the court-yard. These apparitions she knew so intimately that she began to be reassured, and her confidence once restored she reflected that either the spirits must have held her unworthy of a sight of them and have been visible only to the master, or else that the doctor had gone completely out of his mind. Of her own sanity she had no doubts for her mind was made of sterner stuff and would therefore be less easily affected.