A romantic thriller set in the lower depths of 1860's Paris, "In Secret" is a tale of obsessive love, adultery, murder and revenge based on Emile Zola's scandalous novel 'Therese Raquin'.

Sexually repressed, beautiful and young, Therese (Olsen) is trapped in a loveless arranged marriage to her sickly cousin Camille (Felton). Spending her days working behind the counter of the family's small shop with her husband's domineering mother, Madame Raquin (Lange), an occasional dominos night is her only distraction.

When Camille brings home Laurent (Isaac), a charming and handsome childhood friend, Therese is drawn in by his primitive sexuality and overwhelming presence. A secret and risky affair quickly evolves into an insatiable obsession, and Therese is finally alive. Dominated and controlled solely by their lust, they soon plot to remove the only obstacle to their freedom - the unsuspecting Camille.

After a terrible "accident" takes Camille, Laurent quickly assumes his place as Therese's new husband and Madame's loving son. But guilt consumes the murderous pair, their desire unraveling into suspicion and mistrust while they torment each other with threats of confession. Watching as they spiral out of control, Madame comes to realize the horrific truth and Therese must finally face the tragic consequences of her own reckless passion.