This is the continuation of The Mystery of the Yellow Room with many of the main characters reappearing. The setting is even more fascinating in an old castle called The Fort of Hercules. Again we get a detailed map of the castle where the strange happenings occur to help us visualize the setting and situation. The novel explains and resolves some of the connections between the various characters leading to a stunning revelation.
- CHAPTER I: Which Begins Where Most Romances End
- CHAPTER II: In Which There Is Question Of The Changing Humors Of Joseph Rouletabille
- CHAPTER III: The Perfume
- CHAPTER IV: En Route; the Little Orange Fisher
- CHAPTER V: Panic
- CHAPTER VI: The Fort Of Hercules
- CHAPTER VII: Which Tells Of Some Precautions Taken By Joseph Rouletabille To Defend The Fort Of Hercules Against The Attack Of An Enemy
- CHAPTER VIII: Which Contains Some Pages From The History Of Jean Roussel-Larsan Ballmeyer
- CHAPTER IX: In Which "Old Bob" Unexpectedly Arrives
- CHAPTER X: The Events Of The Eleventh Of April
- The Morning
- The Luncheon and What Followed - A Contagious Terror Spreads Through Our Midst.
- How I Spent My Afternoon up to Five O'Clock
- What Happened from Five O'Clock that Night Until the Moment When the Attack on the Square Tower Began
- CHAPTER XI: The Attack Of The Square Tower
- CHAPTER XII: The Impossible Body
- CHAPTER XIII: In Which The Fears Of Rouletabille Assume Alarming Proportions
- CHAPTER XIV: The Sack Of Potatoes
- CHAPTER XV: The Sighs Of The Night
- CHAPTER XVI: Discovery Of "Australia"
- CHAPTER XVII: Old Bob's Terrible Adventure
- CHAPTER XVIII: How Death Stalked Abroad At Noonday
- CHAPTER XIX: In Which Rouletabille Orders The Iron Doors To Be Closed
- CHAPTER XX: In Which Rouletabille Gives A Corporeal Demonstration Of The Possibility Of "The Body Too Many"
1st edition 1909; PDF 214 pages.
word count: 106806 which is equivalent to 427 standard pages of text