Before leaving the hotel, Bob had occasion to go up-stairs, wishing to make sure that nothing belonging to Frank had been left behind.
As he passed through the main corridor, he saw a tall, slim man pass hurriedly to one side and slip into a room the youth knew was vacant.
The actions of the fellow were so peculiar that Bob could not help noticing them, and the more he thought over the matter, the more he became convinced that the slim man was up to no good.
“I’ll watch him for a few minutes and make sure,” said Bob to himself.
He entered the room Frank and he had occupied, and from a crack of the door looked out into the vacant corridor.
A minute passed. Then he saw the slim man emerge from the apartment in which he had sought shelter, and cross to a room opposite.
The door of the room was locked, but the man inserted something, which Bob thought was a wire, into the key-hole, and at once passed inside.
“That’s queer,” said the youth to himself. “I think I’ll investigate a bit further.”
Leaving his room, he tiptoed his way down the corridor until he came to the room which the man had just entered. The door had been closed from the inside, and, by turning the handle gently, Bob discovered that it had also been fastened.
The catch had been turned so that the key-hole was still clear. Bending down, Bob peered through this small aperture.