Number 67 Clarges Street—a good address in London's elegant Mayfair with a dubious past and a lovably eccentric staff—is where the Hart sisters are taking up residence for the season. Beautiful and socially ambitious Euphemia and her younger sister, Jane, enter a world of balls, coming-out parties, and courtship with the hope of finding suitable husbands.

But Number 67 has been deemed unlucky due to a long history of tragedy, including the mysterious death of a young and desirable past tenant named Clara. Little Jane, constantly overshadowed by her gorgeous sister, soon turns away from the London social scene and concentrates on solving the mystery behind Clara's death. Her search leads to a discovery of danger, deceit, and romance as she works alongside the eligible and dashing Lord Tregarthan to unravel the baffling case.