The Iron Gates by Margaret Millar

[paigenumber]

"Lucille Morrow was a fortunate and happy woman.  Though middle-aged, she retained the beauty of youth, her husband, a wealthy physician, was devoted to her, she was mistress of a large and charming house.  Suddenly she was gone.  In one day she changed from a serene and self-possessed woman into a creature dominated by a fear so intense that she gladly committed herself to an asylum - a fear so persistent that it gradually destroyed her mind.  In his search for the cause of her flight, Detective Inspector Sands follows a long trail that takes him into an abyss of horror, murder and inevitable retribution and a degree of cruelty unparallelled in his experience!"

Copyright 1945.

I've read several of Ms. Millar's mysteries and enjoyed them for their twists.  I decided to include this one under Gothic romance, not because it fits into that category very easily, but because I consider it a Gothic suspense.  To say more would be to give the story away.  It could be considered a psychological horror.