My Stepbrother , My Sin

Isolde, heiress to a fallen earldom, has borne the shame of forged heretical letters for two years. When her mother engages to a duke, his marginalized son Gareth, a landless knight, enters her life as a stepbrother and reluctant ally. To defeat her rival Beatrix, Isolde wagers that Gareth can seduce Beatrix.

If he wins, Isolde becomes his prize. But the game turns deadly as Beatrix escalates to attempted murder, and Gareth's every calculated gesture begins aiming at Isolde herself. As danger grows, the wager becomes real love, until their forbidden bond is exposed and the cathedral ceremony becomes public ruin.