Lady Elizabeth Banning, the youngest and most headstrong of the three Banning sisters, is a shameless, hardened flirt with a reputation for jilting fiancés. Perhaps she is reluctant to marry because of her father's appalling treatment of his wives and daughters, or perhaps because she's headstrong and likes to do as she pleases. When a mysterious man helps extricate Beth from a potentially scandalous situation that arises after she throws over another fiancé, Beth doesn't realize she has become a weapon that government-sanctioned assassin Neil Severin can use against her brother-in-law Hugh, the Duke of Richmond.

When Neil attempts to abduct Beth in order to force a confrontation with Hugh, one of her angry former fiancés beats him to it. As Neil rescues Beth from a medieval fortress on the Scottish border, he and Beth escape harrowing dangers and fall in love. And clever Beth comes up with a way to protect Neil from the official death sentence against him - she marries him.