Sera Vasik sits in a royal dungeon, convicted of poisoning a duke. She did it — she just had a very good reason no court would hear. Then the empire's Chief Justiciar, Lord Cael Maren, visits her cell with a proposition: a string of nobles are dying the exact same way, and the Crown's investigators can't identify the toxin. She can. Marry him — a legal technicality that transfers her sentence to house arrest under his authority — and help him catch the real poisoner before the death toll triggers a succession crisis. In return, she gets a full pardon. She expects to be his prisoner with a longer leash. What she doesn't expect is that every victim was connected to the duke she killed, that the real poisoner is using a recipe from her family's journals — ones that were supposed to have been destroyed — and that the Justiciar chose her not because she's the best poisoner he could find, but because his own brother's name is on the killer's list.