at
what you have correctly called the threshold. We explore the entire
structure of the intellect. Our Professor Locke, himself an afflicted
one, is a man of vast erudition--a scholar of an advanced type, a
philosopher whose adventures into the field of psychology and natural
science is widely known. He has charge of the practical work of the
Mercer Institute, and under him its results are positive and unique."

"We have heard of Professor Locke," and, drily, "have seen some of his
work."

"If you had stated your business before--ah--coming in to me," spoke
the doctor, "you might have had an opportunity of consulting him. He
left for his cottage immediately after dining."

"He does not live here, then?"

"Not in this building--no. There is a detached cottage at the far end
of the grounds which he occupies. If you'd like to see him," and the
heavy jowls of the speaker trembled with eagerness, "Haines will show
you there at once."

"If it is no trouble," said Ashton-Kirk, smoothly.

"Not in the least." The doctor rang for his man, and when he entered,
said: "These gentlemen would like to speak to Professor Locke. Show
them the way to his house. And, gentlemen," to the callers, with
anxiety, "the professor can arrange everything with you. It is my
habit to nod for a half hour after dinner. My system has grown to
expect it, and if I am deprived of it, I suffer considerably in
consequence."

"We will not trouble you again, doctor," Ashton-Kirk assured him.
"Thank you, and good-night."

Once more outside, the man led them along a foot-path that seemed to
cut the institution grounds in two. The rays of his lantern danced
along the carefully kept lawn; the shadowy trees seemed to move
backward and forward, as the thin beams wavered among them.

"The professor lives a good piece away," the man informed them. "Away
over on the county road."

"Prefers to be alone, eh?"

"I suppose so, sir. And then he has his laboratory and work-shop
there, well away from interruption. He don't like to be much disturbed
while he is engaged in his studies."

"Few of us do," said Pendleton.

"Quite right, sir."

They walked along in silence for a time; then they caught a clear
humming noise from some distance ahead.

"A motor car," said Pendleton.

"It's on the county road," said the man with the light. "We always
hear them when the wind blows from that direction."

After some fifteen minutes' steady walking they saw a long t