"No one."
"But isn't three in the morning a rather unusual time for you to visit your professors?" Wade asked.
President Ellsworth seemed somewhat perturbed at the question, glancing toward Grantham and then back to the detective. "My reason was a private one, but I have no objection to telling you of it. The fact is that I had become worried over this experiment or theory of Grantham's during the evening. While perfectly aware of his integrity, I realized that this work of his had a touch of the sensational that might reflect upon our institution, and I wanted to ask him to go slowly with the thing until his work was beyond any chance of criticism."
"Natural enough," Wade commented. "And what of this Gray? You said it was just after he left that you were struck from behind?"
"Yes, but that hardly makes him the criminal," said Grantham. "Gray has been absolutely devoted to this work of ours, and though somewhat silent and forbidding is quite reliable."
"You know where he lives?"
"Of course—not a thousand yards from here—in the rooming house diagonally opposite this corner of the campus."
Sergeant Wade turned to one of the blue-clad officers and spoke quickly to him. When the man had left he turned back to the physicist.
"This Gray, though, knew all about your projector just finished, something but a handful of people did. And since he had seen it make a man perfectly invisible, he must have been aware what powers its possession would give anyone who wanted to go in for criminal activities?"
"Anyone would have been aware of that," Dr. Grantham rejoined. "President Ellsworth remarked on it at our demonstration yesterday."