CONTENTS
| CHAPTER | |
| I. | [THE BLACK IMP] |
| II. | [A MYSTERIOUS PACKAGE] |
| III. | [THE THREAT] |
| IV. | [FOLLOWING AMY'S TRAIL] |
| V. | [BEHIND THE PANEL] |
| VI. | [A HOLDUP] |
| VII. | [AN INVITATION TO LUNCH] |
| VIII. | [A BOLD MOVE] |
| IX. | [THE ROBBERY] |
| X. | [HANLEY CRON'S STUDIO] |
| XI. | [A VISITOR] |
| XII. | [THE MISSING WORKMAN] |
| XIII. | [AN EMBARRASSING INTERVIEW] |
| XIV. | [THE MYSTERIOUS AGENT] |
| XV. | [A PUZZLING LETTER] |
| XVI. | [WATCHFUL WAITING] |
| XVII. | ["PRIVATE—KEEP OUT"] |
| XVIII. | [CAPTURED] |
| XIX. | [FIRE!] |
| XX. | [THE SECRET REVEALED] |