On this page of mugshots from the 1920s, I found this one:
Under which is the caption:
When ‘Harry Leon Crawford’, hotel cleaner of Stanmore was arrested and charged with wife murder he was revealed to be in fact Eugeni Falleni, a woman and mother, who had been passing as a man since 1899. In 1914, as ‘Harry Crawford’, Falleni had married the widow Annie Birkett. Three years later, shortly after she announced to a relative that she had found out ‘something amazing about Harry’, Birkett disappeared.
There are photos of her/him in another photo array, this one of female criminals. S/he’s #13.
(“Femme Fatales” seems a misnomer, as that term is usually used to describe a certain type of female criminal.)