The Marchioness originally wanted to find a reason to cancel their agreement, but that reason suddenly appeared by itself. The Marchioness thought Ariana failed in her duty because Ruby was still alive, so she didn't allow Ariana to become the Marquess' concubine.
As a result, Ariana did not have the money to buy medicine, so her mother died because of her illness. The news of her mother's death was a nightmare to Ariana, causing her to miscarry and end up as the prime suspect in the attempted murder of the Marquess' daughter.
"Father did not know Mother asked Ariana to kill you at that time, so if Father knew, Ariana would definitely be used as a scapegoat to clear his wife's name." Lucas sighed. "Therefore, the Marchioness forced Ariana to continue working at the mansion so that she could keep a close eye on her."