At length a final stroke sent the weakened hinges from their fastenings, and the men rushed through the underground passage into the murderer's laboratory.
A hasty, startled glance told them that Murdock was not there.
They started for the stairs and were met by a policeman who was just entering from Murdock's office.
"Have you got him?" asked the detectives in chorus.
"No," replied the policeman surprised; "Mr. Sturgis says he went down here about twenty minutes ago."
"We chased him in from the other end not ten minutes ago."
The policeman hurried down the stairs.
Murdock's valise and package stood conspicuous upon the long pine box. But of Murdock there was no sign.
"Gone!" exclaimed one of the detectives deeply mortified at the thought that his quarry had slipped through his fingers. "Gone! How? Where? He cannot have escaped. He cannot——What is it, Mr. Sturgis?"
He had suddenly caught sight of the reporter, half way up the stairs.