Sarah Mildmay, a young girl from a good family, disguised as a governess, infiltrates the family of Lord Mallow. She suspects that the real lord, Blaine Mallow, is actually dead, and his place has been taken by a vile impostor who has appropriated the title and estate, which should legally go to her, Sarah, fiance. The girl is determined to restore justice and bring the scoundrel to light. . In turn, Blaine (or the person posing as him?) begins to guess about the true purpose of Sarah's appearance at the Mallow family estate. How long can the masquerade last? Each strives to tear off the mask from the other, not noticing that the desire to expose the enemy develops into another, much more tender feeling, which both do not dare admit to themselves. Blaine has a wife and son. Sarah is engaged. What does this double game promise for them and their loved ones?