The year is 1813, and Miss Rosaline Bailey finds herself stuck in London at the height of the social season. Her father, the new Royal Physician, leaves her with Charlotte Prince, Rosaline's childhood friend, to make her debut at court. An impish young woman with a fondness for Shakespeare and mathematics, Rosaline has no desire for romance or marriage, and vows to remain invisible. But when the Queen names Charlotte the Star of the season, and Rosaline the Sapphire, she finds herself attracting the attention of the arrogant, reclusive, and gorgeous Duke of St. Albans...

Rosaline and the Duke make a bargain - to form a false but believable attachment, so they can both escape the season unwed. They form an unlikely and fierce friendship, tested only by the caustic, gossip-ridden waters of London. Rosaline finds herself pulled into a heady, unexpected romance - and into a sinister plot that threatens the lives of everyone around her, even the people she holds most dear...