The aristocratic and well-to-do lady, Lina Flerianou, abandons her strict husband and her baby boy for the sake of her young lover. Dishonoured and desperate, Lina, now entangled in her paramour's shady business, returns to Greece after spending two decades in the United States, only to realise that he has set his sights on blackmailing her former husband. Now, as one thing leads to another, after a fierce confrontation, Lina finds herself standing trial for murder. Intrigued by this case, the young lawyer, Alkis, decides to help the cryptic woman, unbeknownst to him, however, that she is harbouring a shocking secret. But, who is the pained woman in black? Will mysterious Madame X ever find forgiveness?