"You will know him when you see him again?"
"Oh, yes."
"Then take your position by the elevator, and if you see him come down, signal to the detective whom I will also station there. He will take care of him."
Ten minutes later the elevator reached the office floor. Among those who stepped out was the young man, wearing an overcoat considerably too large for him. It was clear that he had put it on in No. 58, and was now about to wear it out of the hotel.
He stepped out of the elevator, and with a slight glance about him made briskly for the door. But he had taken only two steps when Rupert caught him by the arm.
"I want to see you a minute," he said.
"I am in a hurry. I have an appointment. I will see you on my return."
But the detective had now stepped forward.
"You will have to stop now," he said, firmly.