Mariah first appears in Genoa City, hired by Victor Newman to gaslight his former daughter-in-law Sharon Newman by posing as the ghost of Sharon's deceased daughter, Cassie, with whom she bears a remarkable resemblance. When the truth about her association with Victor is revealed, Sharon becomes drawn to a troubled Mariah, whom she moves into her home. Meanwhile, it is revealed that Mariah is the notorious ex-girlfriend of Tyler Michaelson; she is also linked to cult leader Ian Ward. While living with Sharon and Nick Newman, Cassie's adoptive father, Mariah develops an infatuation with Nick. It is soon discovered that Mariah is actually Cassie's twin sister and the daughter Sharon did not know she had. Her birth was kept secret, following Ian's arrangements for Mariah to be stolen at birth, and acted as a father figure to her for years. Mariah subsequently has relationships with Kevin Fisher—a dynamic which allowed Grimes to explore comic relief—and Devon Hamilton. She then develops feelings for her brother's girlfriend, Tessa Porter.
