Van Heerden had gone.
The explanation flashed upon him and he hurried to the spot where the doctor had stood.
On the tessellated floor was a little patch no bigger than a saucer which had been recently washed.
He beckoned the manager.
"Who has been cleaning this tile?" he asked.
The manager shrugged his shoulders.
"It was the doctor, sare—so eccentric! He call for a glass of water and he dip his handkerchief in and then lift up his foot and with rapidity incredible he wash the floor with his handkerchief!"
"Fool!" snapped Beale. "Oh, hopeless fool!"
"Sare!" said the startled manager.
"It's all right, M'sieur Barri," smiled Beale ruefully. "I was addressing myself—oh, what a fool I've been!"
He went down on his knees and examined the floor.
"I want this tile, don't let anybody touch it," he said.
Of course, van Heerden had stood because under his foot he had crushed the digitalis tablet he had taken from the phial, and for which he had substituted something more deadly. Had he moved, the powdered tablet would have been seen. It was simple—horribly simple.
He walked slowly back to where he had left Oliva.
What followed seemed ever after like a bad dream to the girl. She was stunned by the tragedy which had happened under her eyes and could offer no evidence which in any way assisted the police in their subsequent investigation, the sum of which was ably set forth in the columns of the Post Record.
"The tragedy which occurred in the Palm-Court of the Grand Alliance Hotel yesterday must be added to the already long list of London's unravelled mysteries. The deceased, a man named Jackson, has been staying at the hotel for a week and was on the point of departure for Canada. At the last moment Dr. van Heerden, who was assisting the unfortunate man, discovered that Jackson was no other than the
