Bombay, 1896. A handsome Indian Prince loses his heart to a European woman of striking beauty. She is staying at the only hotel fit for Europeans— Watson’s, in the elite Kala Ghoda area of the city. The Prince gifts his lady love a necklace of gold set with a beautiful sapphire of so deep a blue that it is known as the Kala Ghoda. But then Fate intervenes. An epidemic of the plague sweeps the city and the lady sets sail for Paris without even bidding goodbye. Before her ship sails, she returns the Prince’s gift through his groom, Madan. When the jewel case is opened, the necklace is there, but the sapphire is not. Madan is accused of the theft, and hanged. The Prince loses his lady and, in years to come, his fortune.

The sapphire appears to have fulfilled its prophecy—that it will bring misfortune to anyone who possesses it. The groom is forever known as ‘Madan Chor’, and the scandal follows his family for four generations.

To find a jewel that has gone missing for 125 years seems an impossible task—even for Lalli. She finds unexpected help in Jean Claude, the retired Chief of Police from Paris, who is here to investigate l’affaire du cheval noir— an investigation begun more than a century ago by Edmund Locard, the legendary detective. It was Locard who was originally engaged to find the sapphire.

It is up to Lalli and Jean Claude to finish the task Locard began. And, despite the re-emergence of Lalli’s old enemy, Rassiwala, and his evil designs—this is what they achieve. Not for nothing is Lalli, long retired, still the Last Resort for the Mumbai Police.