A young lady accused of theft and the gentleman who elects himself her champion enlist the aid of Stokes, Barnaby, Penelope, and friends in pursuing justice, only for the investigators to find themselves tangled in a web of interfamily tensions and secrets.

When Miss Cara Di Abaccio is accused of stealing the Carisbrook emeralds by the infamously arrogant Lady Carisbrook and marched out of her guardian's house by Scotland Yard's finest, Barnaby Adair's cousin Hugo Adair takes umbrage and descends on Scotland Yard, breathing fire in Cara's defense.

Hugo discovers Inspector Stokes has been assigned to the case, and after surveying the evidence thus far, Stokes calls in his big guns when it comes to dealing with investigations in the ton - namely, the Honorable Barnaby Adair and his wife, Penelope.

Soon convinced of Cara's innocence and, given Hugo's apparent tendre for Cara needing to clear her name, Penelope and Barnaby join Stokes and his team in pursuing the emeralds and, most importantly, who stole them.

But the deeper our intrepid investigators delve into the Carisbrook household, the more certain they become that all is not as it should be. Lady Carisbrook is a harpy, Franklin Carisbrook is secretive, Julia Carisbrook is overly timid, and Lord Carisbrook, otherwise a genial and honorable gentleman, holds himself distant from his family. More, his lordship attempts to shut down the investigation. And Stokes, Barnaby, and Penelope are convinced the Carisbrooks' staff are not sharing all they know.

Meanwhile, appointed Cara's watchdog until the mystery is resolved, Hugo, fascinated by Cara as he's been with no other, seeks to entertain and amuse her...and, increasingly intently, to discover the way to her heart. Consequently, Penelope finds herself juggling the attractions of the investigation and the Adair family's demands for her to actively encourage the budding romance.

What would her mentors advise? On that, Penelope is crystal clear.

Aided by Griselda, Violet, and Montague and calling on contacts in business, the underworld, and ton society, Penelope, Barnaby, and Stokes battle to peel back each layer of subterfuge and, step by step, eliminate the innocent and follow the emeralds' trail....

Yet instead of becoming clearer, the veils and shadows shrouding the Carisbrooks only grow murkier...until, abruptly, our investigators find themselves facing an inexplicable death, with a potential murderer whose conviction would shake society to its back teeth.