A disgruntled young chemist. A reformed noble thief. A cranky, middle-aged lord. What could possibly go wrong?

Apprentice chemist Iggy's uncle won't sign her off as competent, even though he trusts her with Project Sapphire: researching a formula to erase forensic evidence. When she finds an alternative route to sign-off, she applies her energy to that, neglecting her assigned duties to do so. In a stroke of luck, this decision leads her to a sponsorship deal, but her benefactor has secrets she's unaware of.

After his recent adventure abroad, Lord Richard Hayes is now home: and on probation to keep his seat on the Council of Lords. He has plentiful funds, detailed instructions and a boring plan for honest living, but despite his efforts to fit in, everything starts to go wrong. He loses his only household servant, he antagonises a young chemist the first time he meets her, and he gets blamed for a burglary he didn't even do. The only bright spot is that making new enemies keeps life from being completely dull.

Stiff-necked Lord Huntley Angus detests frivolous young nobles who dodge responsibility for their actions. But when he secretly pawns his wife's jewellery to pay an unexpected debt, he gets entangled in a spiralling set of misfortunes.

The Sapphire Solution is a fantasy of manners that takes place immediately after the events of The Diamond Device.