However, he knew that he had actually become a somnambulist; for twice at night his room had been found vacant, though with all his clothing in place. Of this he had been assured by Frank Elwood, the one fellow-student whose poverty forced him to room in this squalid and unpopular house. Elwood had been studying in the small hours and had come up for help on a differential equation, only to find Gilman absent. It had been rather presumptuous of him to open the unlocked door after knocking had failed to rouse a response, but he had needed the help very badly and thought that his host would not mind a gentle prodding awake. On neither occasion, though, had Gilman been there; and when told of the matter he wondered where he could have been wandering, barefoot and with only his night clothes on. He resolved to investigate the matter if reports of his sleep-walking continued, and thought of sprinkling flour on the floor of the corridor to see where his footsteps might lead. The door was the only conceivable egress, for there was no possible foothold outside the narrow window.