Fergus Hume 
The Secret Passage 

The Secret Passage is a fantastic murder mystery by Fergus Hume. It has contrived another of his hide-and-seek, jack-o'-lantern murder mysteries. The story starts with an elderly, wealthy, and queer woman who was found stabbed to death on her chair with no sign of the culprit. Then, there are so many new clues that even the fictional investigator is perplexed. Then almost everyone is shown to be someone else using an alias, and all the leads are in vain.Young Susan Grant, who is looking for work, turns up at Miss Loach's house, Rose Cottage. Susan is hired as a parlor maid after a quick but intensive interview, and she soon learns about the high expectations Miss Loach has for her staff. Her sister Mrs. Octagon, a self-promotional writer who lives across the street with her husband Peter and daughter Juliet, is a writer. One day, after having afternoon tea with Juliet, Mrs. Octagon brings up her sister, whose peaceful existence she much disapproves of. Her husband unexpectedly enters the room at this precise time with the news of Miss Loach's murder.Was it Susan, whose prior experience working for a shady Spaniard seems dubious at best? Was it Mrs. Octagon, who always reacted with the worst of insults when she brought up her sister?