Rosalind Thorne's quick wits and discretion have proved invaluable to London's haut ton. Success has at last brought her financial stability and a new home, which she shares with her best friend, Alice Littlefield. But now trouble has infiltrated Rosalind's sanctuary, and the reputations in danger include her own.

Alice has formed a tender attachment to Amelia, the maid in their employ, and her affection is returned. But before meeting Alice, Amelia was involved with Cate Levitton, daughter of a well-respected family. The scandalous liaison caused the Levittons to banish Cate to the house of her widowed cousin. Amelia has no expectation of seeing Cate again—until she stumbles upon her in the marketplace, looking deathly ill.

The women bring Cate to their home with the help of Bow Street officer Adam Harkness, who deduces that Cate's sickness may in fact be arsenic poisoning. But who had motive, or means? As Rosalind and Adam work side by side, their suspicions grow—as does the bond between them. Rosalind knows that both her blossoming relationship with Adam and her increasing independence would be frowned upon by society. Poison, politics, jealousy and jewel thieves combine in Rosalind's most complex case yet. But to solve this dangerous puzzle, Rosalind must also decide where her heart and her future lie . . .