You Are My Lighthouse

In order to take revenge for her mother, the heroine pretends to be insane and marries into the Ford family with plans to destroy them. Upon discovering that the sickly heir was poisoned by his uncle and aunt, she switches sides and secretly cures him. A red mole raises his suspicions; he investigates her past and becomes sympathetic towards her. Together they prevent further schemes from happening. When her family tries to swap her back, the mistress's daughter attempts to seduce the heir but is caught in action and ends up with the cousin.