Black Coffee by Jeffery Farnol

-"I wish," said the Professor, as he took up his pen, "I wish that I had not let John go, I feel strangely lonely to-night, and John is so very matter of fact," so saying he bent to his writing again. His brain had grown singularly bright and clear, all his faculties seemed strung to their highest pitch, a feeling of exaltation had taken possession of him. His ideas grew luminous, intricate thoughts became coherent, the words shaping themselves beneath his pen with a subtle power and eloquence.

Yet all at once, and for no apparent reason, in the very middle of a sentence, a desire seized upon him to turn his head and look back over his shoulder at that which stood in the corner. He checked it with an effort, and his pen resumed its scratching; though all the time he was conscious that the desire was growing, and that sooner or later it would master him. Not that he expected to see anything unusual, that was absurd, of course. He began trying to remember how many screws there were holding down the lid upon that Thing, whose lips had mocked at God and man through centuries and whose eyes--ah, whose eyes---- The Professor turned suddenly, and with his pen extended before him, began counting the glinting screw-heads to himself in an undertone.