Odetta Holmes is one of the alternate personalities of Susannah Dean. Odetta was the original name that the woman was born with. She was a kind civil rights activist, in contrast to Detta Walker. At the end of The Drawing of the Three, Odetta and Detta Walker were forced to recognize each other's existence and combined to create the personality of Susannah.
During her time as Odetta, Susannah was the daughter of Daniel Holmes, a very wealthy and important black man. This allowed Odetta to live a better life compared to other blacks of her time, but her life was still riddled with personal tragedy. When she was eight, Jack Mort dropped the brick on her head that would cause the personality split of Detta Walker to come forward.
Later, Jack Mort would strike again, pushing her in front of a train at Christopher Street Station, causing Odetta to lose her legs. Her final embarrasment would come when white supremacists locked her in a cage.
The Drawing of The Three
When Roland Deschain enters the door to 1964 and drags her into Mid-world, Detta Walker is in control and responds in a hostile manner, calling him a "honky mahfah". Odetta Holmes's personality finally wakes up and tries to dismiss the whole incident as a dream, but eventually realizes the reality of the situation and becomes depressed and hysterical. She eventually finds friendship and love in Eddie Dean, another person drawn from her world; however, the relationship is restricted by Detta's personality who hates him utterly.
Detta takes over and escapes when Roland travels through the third door into the mind of Jack Mort. Eddie is left alone in the darkness with Detta, who intends to murder him and Roland. She eventually holds Eddie up with Roland's gun and ties him up in ropes. She leaves him on the beach to get eaten by lobstrosities.
Roland (in Mort's body in Detta's world) realizes a way to save Odetta's life, and brings Mort down to a subway station. He calls for both Odetta and Detta to look into the doorway out of Mort's eyes. When they both look into the doorway, they see each other for the first time and both have combined memories of Mort dropping the brick on their head and then being pushed in front of the train. This has the effect of blending the personalities together, creating Susannah Dean (Susannah as it was both their middle names, and Dean as she is married to Eddie by ka).