Stella returned to the entrance of the vault and placed a padlock and chain on its iron door while Ackerman again entered the underground passage and spent two hours alone, making the most minute examinations and measurements of every track to be found at any point from the door of the vault to the panel in the wainscoting. The work of measurement was rendered easy by the accumulation of soft earth in the bottom of the underground way from the action of the water which had soaked through the brick ceiling and walls.
He discovered the footprints of eleven different men besides the dainty mark of Stella's little shoe made the night before.
He returned to the hall and asked her permission to come from time to time and continue his study of the grounds.
"Certainly," she answered eagerly. "And your discoveries?"
"Confirm so far my theory of the crime," he answered quickly. "The assassins undoubtedly entered the house by this secret passage, committed the crime and passed quickly out without discovery. I did not know who was with you last night, but he has been there at least once before within the past few weeks."
"Is it possible!" Stella exclaimed.
"I find," he continued, "that he merely took
