"The Affair at the Semiramis Hotel" by A. E. W. Mason is a detective novella published in 1917. When a fashionable young man arrives at his friend's breakfast table with a desperate tale, Inspector Hanaud must determine whether the story is real or drug-induced hallucination. A masked ball, a stolen pearl necklace, a murdered guest, and a terrified opera singer who claims she witnessed the crime—all lead to a theatrical trap that unmasks a killer hiding in plain sight. (This is an automatically generated summary.)