The Guardian's Dilemma (The Steepwood Scandal, Book 11) (Harlequin Historical Series #113)

In an effort to save his young stepsister from a fortune hunter's grasp, Oliver Brandon places her in a genteel ladies' academy. His shock is considerable when he realizes that one of the respectable schoolmistresses is a woman he last saw at a house party -- in a highly compromising situation! It's obvious to Helen de Coverdale that Oliver Brandon has serious misgivings about handing his ward into her charge. But will he listen if she tries to tell him her side of the story...?