The thing is quite apparent.

Von Behrling never succeeded, after all, in shaking off the espionage of the men who were watching him.

They tracked him to our rendezvous, they waited about while I met him.

Afterwards, he had to pass along a narrow passage.

It was there that he was found murdered." "But, David, I don't understand! Why did they wait until after he had seen you?
How did they know that he had not parted with the paper in the restaurant?
To all intents and purposes he ought to have done so." "I cannot understand that myself," Bellamy admitted.