Summary
The narrator is sitting over a vermouth outside the Café de la Paix when Lord Murchison, a friend from Oxford known for his frankness and his firm Tory beliefs, calls his name. Gerald seems changed, and says that he cannot love where he cannot trust. During a drive he shows the narrator a photograph of a tall, slight woman in rich furs, with large vague eyes and a faint, subtle smile, whom the narrator calls 'the Gioconda in sables'. After dinner Gerald tells her story.
He first sees her face in a yellow brougham in Bond Street and hunts for it in vain until, a week later, she arrives late at a dinner given by Madame de Rastail and is announced as Lady Alroy. When he mentions having seen her in Bond Street she turns pale and begs him to speak more quietly. She lets him call, but is out when he arrives; later she asks him to write to her only as 'Mrs. Knox', care of a library in Green Street. All season her air of mystery draws him on, and he decides to ask her to marry him.
On the Monday of the proposal, taking a shortcut through shabby streets near the Marylebone Road, he sees her, deeply veiled, let herself into a lodging house with a latchkey, and he picks up the handkerchief she drops on the step. At six she tells him she has not been out all day. Shown the handkerchief, she bursts into tears, but insists that there is nothing to tell and that she went to meet no one. He says terrible things, rushes out, returns her next letter unopened and goes to Norway. A month later he reads in the Morning Post that she has died of a chill caught at the Opera.
Tortured with doubt, he visits Cumnor Street. The landlady recognises the photograph and says the lady paid three guineas a week merely to sit in her drawing-rooms, always alone, reading books and sometimes taking tea. The narrator believes her. Lady Alroy, he says, had a mania for mystery and took the rooms for the pleasure of going there veiled and imagining herself a heroine: she was 'a Sphinx without a secret'. Murchison opens the morocco case, looks at the photograph again and says only, 'I wonder?'