Irene Adler

Origin
According to "A Scandal in Bohemia," Adler was born in New Jersey in 1858. She followed a career in opera as a contralto, performing at La Scala in Milan, Italy, and a term as prima donna in the Imperial Opera of Warsaw, Poland, indicating that she was an extraordinary singer (in reality, there was no Imperial Opera in Warsaw). It was there that she became the lover of Wilhelm Gottsreich Sigismond von Ormstein, Grand Duke of Cassel-Felstein and King of Bohemia, who was staying in Warsaw for a period. The King describes her as "a well-known adventuress" (a term widely used at the time in ambiguous association with "courtesan") and also says that she had "the face of the most beautiful of women and the mind of the most resolute of men." The King eventually returned to his court in Prague. Adler, then in her late twenties, retired from the opera stage and moved to London.

On 20 March 1888, the King makes an incognito visit to Sherlock Holmes in London. He asks the famous detective to secure a photograph of Adler and him together. The 30-year-old King explains to Holmes that he intends to marry Clotilde Lothman von Saxe-Meningen, second daughter of the King of Scandinavia; the marriage would be threatened if his prior relationship with Adler were to come to light. He also reveals he had hired burglars to attempt to retrieve it twice, had Adler herself waylaid, and her luggage stolen, to no avail.

Using his considerable skill for disguise, Holmes traces her movements, learning much of her private life and, notably, stands witness to her marriage to Godfrey Norton, an English lawyer. Holmes then disguises himself as an elderly cleric and sets up a faked incident to cause a diversion that is designed to gain him access to Adler's home and to trick her into revealing where the picture is hidden. Adler treats him, as the supposed victim of a crime outside her home, with spontaneous care and solicitude. At the moment she gives away the location of the photograph, she realizes she has been tricked. She tests her theory that it is indeed Holmes, of whom she had been warned, by disguising herself as a young man and cheekily wishing him good night as he and Dr. Watson return to the Baker Street flat.

When Holmes returns the next morning with Watson and the King to demand the return of the photograph, he finds Adler gone, along with her new husband and the original photo, which has been replaced with a photograph of her alone as well as a letter to Holmes, explaining how she had outwitted him, but also that she is happy with her new husband, who has more honourable feelings than her former lover. She adds that she will not compromise the King and has kept the photo only to protect herself against any further action the King might take. In the face of this and the King's arrogant statement that it was a "pity that she was not on my level", Holmes realizes then that Adler was the wronged party rather than the King and asks, when offered a reward by the King, only for the photograph that Adler had left.

At the time that Conan Doyle meant Watson to be writing the story. it is clear that Irene has passed away, since she is referred to as 'the late Irene Adler.'