Publisher's Synopsis
The story is set in London, after the events described in At the Villa Rose. Ricardo, the dilettante amateur detective, is sitting at his breakfast table in Grosvenor Square when he is interrupted by his great friend Gabriel Hanaud, the French professional detective.A visitor is unexpectedly shown in: a fashionable young man named Calladine whom Ricardo has not seen for several months. Visibly distressed, Calladine blurts out a fantastic tale of having attended a ball at the Semiramis Hotel the night before, and having met a young woman dressed in a distinctive masquerade costume who had early the next morning turned up unannounced at his chambers seeking sanctuary. He reports that the young woman, Joan Carew, an opera singer, confessed that she had been tempted by a valuable pearl necklace worn by one of the hotel guests, and that she had crept into her room to try to steal it. On entering, she finds that she had inadvertently disturbed and been seen by two masked men who were also there to steal the pearls. She faints, and when she comes round discovers that the men have disappeared and she is alone with the necklace's dead owner. She rushes over to Calladine's chambers.Hanaud and Ricardo accompany Calladine across town to his chambers, and initially conclude that he imagined the whole thing when they discover that he is a user of the drug mescal, known for its ability to create colourful hallucinations. But then the newspapers report the crime. Joan Carew repeats her story to the two men, and later tells them that in a dream she thought she saw the mask of one of the thieves slip so that she could see his face. The unmasked man is André Favart, companion of the opera star Carmen Valeri, one of Joan Carew's professional colleagues.With the assistance of the director of the Opera House, Hanaud gets Joan Carew to sing her role in that night's production dressed in the distinctive costume she was wearing when she had disturbed the thieves. Then, after the performance, he arranges for Favart to bump into her. When Favart realises who she is, and that he has been recognised, he attempts to run but is detained and arrested for murder. The stolen necklace has been hidden in plain sight amongst the paste jewellery worn on stage by the unknowing Carmen Valeri.Calladine and Joan Carew are soon married.
