or's."

The two men drove to the outskirts of the city almost in silence, while
several of the officers followed in another taxi. The Professor's house
seemed more than ever deserted as they drew up at the front door. They
entered without ringing and crossed the hall towards the library. On the
threshold Quest paused and held up his finger.

"Some one is in there," he whispered, stepping quickly forward. "Come!"

He threw open the door. The room was empty, yet both Quest and French were
conscious of a curious conviction that it had been occupied within the
last few seconds. French even shook out the curtains and swung open the
doors of a bureau. There was no sign of anybody, however, nor any evidence
as to how they could have left the room.

"Queer, but it seemed to me I heard some one," French muttered.

"I was sure of it," Quest replied, shaking the curtains at the back of the
door.

They stood still for a moment and listened. The silence in the empty house
was almost unnatural. Quest turned away with a shrug of the shoulders.

"At any rate," he said, "Craig's dying thoughts must have been truthful.
Come."

He led the way to the fireplace, went down on his knees and passed his
hands over the bricks. The third one he touched, shook. He tapped
it--without a doubt it was hollow. With his penknife he loosened the
mortar a little and drew it out easily. The back was open. Inside was the
black box.

"Craig's secret at last!" French muttered hoarsely. "Bring it to the
light, quick!"

They were unemotional men but the moment was supreme. The key to the
mystery of these tragical weeks was there in their hands! Their eyes
almost devoured those few hastily scrawled words buried with so much care:

_See page 62, January number, American Medical Journal 1905._

They looked at one another. They repeated vaguely this most commonplace of
messages. As the final result of their strenuous enterprise, these cryptic
words seemed pitifully inadequate. Quest's face darkened. He crumpled the
paper in his fingers.

"There must be some meaning in this," he muttered. "It can't be altogether
a fool's game we're on. Wait."

He moved towards a table which usually stood against the wall, but which
had obviously been dragged out recently into the middle of the room. It
was covered with bound volumes. Quest glanced at one and exclaimed softly.

"_American Medical Journal, 1905!_ French, there's something in this
message, after a