Passage: World-famous opera singer Alice Alquist has just been murdered at her home, No.9 Thornton Square. The perpetrator left without the jewels he sought after being interrupted by Paula, Alice's fourteen-year-old niece.  Paula was raised by her aunt following her mother's death.  After Alice is murdered, Paula is sent to Italy to train to become an opera star herself.
Years later, an adult Paula meets and marries Gregory Anton after a two-week-long whirlwind romance.  Paula returns to London on his insistence, where she knows no one, to live in the long-vacant London townhouse of her deceased aunt Alice. To help calm her anxieties, Gregory suggests they store all of Alice's furnishings in the attic. Before they do, Paula discovers a letter in an old book addressed to her aunt by a man named Sergius Bauer.  Gregory's reaction is violent.  However, he dismisses his outburst as one of frustration at the bad memories his bride is experiencing.
After Alice's belongings are locked away in the attic, events take a turn for the bizarre. At the Tower of London, Paula loses an heirloom brooch that Gregory had given her, despite its having been stored safely in her handbag. A picture disappears from the walls of the house; and Gregory says that Paula took it, one of many instances of her removing and hiding it.  But Paula has no recollection of having done so. Paula also hears footsteps coming from  the sealed attic, and sees the gaslights dim and brighten for no apparent reason. Gregory suggests these are in her imagination.
What is the full name of the man that niece of the opera singer marries?