Themes
The love of mystery
Murchison says that at the time he thought he loved Lady Alroy in spite of her mystery, but now sees that he loved her because of it. Her secrecy is what holds him: the low voice at dinner, the letters addressed to 'Mrs. Knox', the veil. The twist is that the mystery is empty. Lady Alroy took rooms in Cumnor Street only to sit there alone and feel like a heroine. Wilde suggests that mystery is a pleasure in itself, for the person who makes it and for the person who tries to solve it, and that it needs no content at all.
Truth and trust
Murchison's friends used to say he would be the best of fellows 'if he did not always speak the truth', yet he cannot recognise the truth when he hears it. 'I cannot love where I cannot trust,' he says, and his distrust destroys the one thing he wanted. When Lady Alroy tells him that there is nothing to tell and that she went to meet no one, she is speaking plainly, as the landlady later confirms. His certainty that there must be another man makes him cruel, and he sends her last letter back unopened.
Faces and pictures
The whole story turns on a photograph. The narrator reads the face as that of 'someone who had a secret', with a beauty that is 'psychological, not plastic' and a smile 'far too subtle to be really sweet', and he names her 'the Gioconda in sables', after the most famous enigmatic smile in painting. Murchison keeps the photograph in a silver-clasped morocco case and shows it to the landlady as proof. The subtitle, 'An Etching', fits: this is a small sketch in black and white, in which a face promises more than the life behind it holds.
Men reading women
The story opens with the narrator's quip that 'women are meant to be loved, not to be understood', and everything that follows is men trying and failing to understand a woman. Murchison supposes that she is 'in the power of some man'; a scientific bore at dinner lectures on widows as 'the survival of the matrimonially fittest'; the narrator settles the case with easy confidence. Lady Alroy herself never explains. The only account of what she did in Cumnor Street comes from her landlady, and the men are left to supply the rest.
Certainty and doubt
The narrator has no doubts. 'I am sure of it,' he replies, and his solution is neat and witty. Murchison is not so easily satisfied. The story ends with him opening the morocco case once more and asking 'I wonder?', which leaves the reader poised between the two men. Perhaps Lady Alroy really had no secret; perhaps the narrator's cleverness is as shallow as Murchison's suspicion was unjust. Wilde closes the tale on a question mark, so that the reader, like Murchison, is left looking at the photograph.